Postage Calculator by Weight

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March 17, 2024

Domestic USPS (United States Postal Service) mail or packages weighing over 70 pounds (lbs) are considered nonmailable and subject to overweight charges.

Say your parcel exceeds the maximum weight limit (70lbs) but got mailed anyway. In that case, you will pay extra for the package’s overweight status before you or the addressee can retrieve it.

However, if the overweight package gets discovered at the same facility where you dropped it off, USPS won’t charge you an additional fee. 

Meanwhile, USPS will require you to pay additional postage if your package exceeds the weight you informed the carrier.

These scenarios highlight the significance of determining your package’s weight and the appropriate mailing service before handing it to your local post office.

So, what are the rates for various USPS options? How do you calculate delivery costs based on the parcel’s weight and size?

This article discusses calculating postage by weight and using USPS’ postage calculator to help you understand how it computes delivery costs.

Learn more about USPS shipping rates. FindPostOffice.org is your go-to online resource for crucial information regarding post offices in the U.S., including how to use postage calculators.

How Do You Calculate Postage by Weight?

USPS features various retail postage calculators on its website. One calculator determines delivery costs based on weight, size, and shape.

The calculator asks the following questions:

  • What unit of measurement do you use?
  • What is your mail piece’s weight?

You will also have to choose any of the following package and mail items to view suggested mailing services:

More About Dimensional Weight

Dimensional (DIM) weight indicates the amount of space a package takes up in a plane or truck during shipping.

The dimensional weight price may apply to items shipped via these mail classes:

  • Priority Mail
  • Priority Mail Express 
  • USPS Ground Advantage (excludes Limited Overland Routes parcels) 
  • Parcel Select (excludes Parcel Select Lightweight) 

Note: The price calculation differs depending on the mail class.

Here are additional things to consider regarding the DIM weight price:

  • DIM weight price for low-density shipments to Zones 1-9: For the domestic mail classes above, postage for parcels sent to Zones 1-9 and that exceed 1,728 cubic inches (one cubic foot) reflects the actual weight or the calculated DIM weight, whichever is greater. 

Note: If the DIM weight exceeds 70lbs, postage is based on the 70-pound price.

  • DIM weight price for Global Express Guaranteed (GXG): USPS prices for items not shipped in GXG envelopes depend on the calculated DIM weight or the actual weight, whichever is greater

“How Do I Calculate My Postage?”

You can calculate your postage using USPS retail or business price calculators for domestic and international shipments.

The following sections discuss how to use a USPS postage or shipping calculator.

USPS Shipping Calculator

The easy-to-use tool allows customers to specify shipment details, such as destination, dates, ZIP codes, service level, and weight, to compare costs and delivery times.

How to Use the USPS Shipping Calculator

Using the USPS shipping calculator, you can know the potential shipping cost for your preferred mailing service. This online tool is ideal for estimating and budgeting for delivery charges. 

The calculator also eliminates any guesswork regarding shipping rates and lets you compare shipping options conveniently.

The section below lists eight steps you can take to use the USPS postage calculator:

Use The Calculator From USPS to Determine Shipping Costs

Here’s how to operate the USPS shipping calculator:

  1. Visit the USPS postage price calculator page: This page lets you calculate shipping rates for domestic and international deliveries.

Suppose your business mailings are presorted. In that case, you can determine your shipping expenses via the USPS business price calculator.

  1. Specify letter or package details: Identify the destination of your mail or package from the drop-down menu. Then, provide the following information:
  • Your and your recipient’s five-digit ZIP codes
  • Mailing date and time
  • The content of your envelope or package
  1. Select the delivery method: After providing the details above, you will choose a USPS shipping method.

The calculator lets you select a Flat Rate option or a shape like a package, postcard, large envelope, letter, or large package.

Once you’ve entered your shipment details, you must decide how to ship it to its destination. 

Suppose you select a flat-rate option, such as the Priority Mail medium Flat Rate box. In that case, you can view the expected delivery date and the retail and online postage prices.

Meanwhile, say you choose a letter. The system will request you to provide your letter’s weight.

Click “Continue” to select a shape that best fits your letter.

  1. Compare delivery options: You will now see the rates for your chosen shipment type. 

You can compare shipping costs by clicking “Display All Options” at the top of the page.

  1. Purchase extra services (if applicable): Here, you can buy additional services, such as Insurance, Certificate of Mailing, or Registered Mail.
  2. Press “Continue” to see the result: The page will display the total shipping cost to ship your mail or package to its destination.
  3. Pay for shipping and print the required postage: Visit the USPS Click-N-Ship (CNS) page to purchase shipping and get postage.

CNS is a program for residential and small business customers to order and print postage labels online.

Meanwhile, you will use an online postage service, like Stamps.com, to print postage for the following mailing services:

  • Media Mail
  • First-Class Package Service
  • Parcel Select Ground
  1. Check shipping rates on Stamps.com and print your postage: Stamps.com can help determine the postage for all your shipments, so no more guesswork. 

Stamps.com’s Best Rate shopping engine tool helps you find the ideal shipping rate based on predetermined factors like box size and delivery time preferences. 

Using Stamps.com’s shipping calculators, you can estimate postage for your packages and letters.

About the USPS Priority Mail Shipping Rate Calculator

You can use the retail postage price calculator to determine your domestic postage costs. The Priority Mail page links to this tool for calculating Priority Mail postage rates.

This service delivers in one to three business days and offers tracking details. 

Suppose you want to know the estimated delivery time for shipping to a particular location. In that case, you can use the Priority Mail Delivery Map.

Follow these steps when using this tool:

  • Enter the three- or five-digit ZIP code you’re shipping from.
  • Drag and zoom the map to view the mailing area, including Alaska, Hawaii, and U.S. regions eligible for Priority Mail service.

Priority Mail Flat Rate options let you ship items up to 70lbs to any state at the same rate. You can ship from post office locations or online from your business or home.

Here are the primary features of Priority Mail:

  • You can access the no-cost Package Pickup service at your office or home.
  • Priority Mail provides USPS Tracking and up to $100 worth of insurance for most deliveries (restrictions apply).
  • Prepaid Forever Priority Mail Flat Rate allows you to get the same flat-rate pricing with the added benefit of Forever postage.
  • Except for Priority Mail Flat Rate shipments, Priority Mail prices depend on zone and weight.
  • There are no additional fuel, rural, residential, or Saturday delivery fees.
  • Priority Mail offers flat rates and prepaid retail pricing.
  • Priority Mail prints and delivers outbound labels to users via CNS for an extra $1.25 per label.

Using the Priority Mail Calculator

You must provide the Priority Mail calculator with the answers to the following questions:

  • What is the destination country?
  • What ZIP code are you mailing from?
  • What ZIP code are you mailing to?
  • What’s the date you plan to mail the item?
  • What time do you plan to mail the item?
  • What are you sending?
  • Does the mailpiece need ground transportation?

After inputting your answers, you will choose from four options:

  • View flat-rate envelopes.
  • Calculate the postcard price.
  • View flat-rate boxes.
  • Calculate the price based on size and shape.

Access Low USPS Shipping Rates and More

Depending on your package’s size, weight, dimension, and destination, some services may be more affordable. 

The following sections discuss these services to help you determine which one is ideal for your item.

USPS Shipping Services

USPS offers the following delivery services:

  • Domestic deliveries
    • Priority  Mail
    • Priority Mail Flat Rate Envelope
    • Priority Mail
    • Priority Mail Express
    • Prepaid Forever Priority Mail Flat Rate
    • Priority Mail Express Open and Distribute  Service
    • USPS Ground Advantage Return
    • Every Door Direct Mail – Retail
    • Parcel Select
    • USPS Connect Local
    • Priority Mail Express Flat Rate Envelope
    • Priority Mail Open and Distribute Service
    • USPS Ground Advantage
    • First-Class Mail
    • USPS Marketing Mail
    • Media Mail
    • Priority Mail Express Return
    • Priority Mail Return Service
    • Library Mail
    • USPS Connect Local Mail
    • Parcel Select Lightweight
  • International shipments
    • Priority Mail International
    • Priority Mail Express International
    • Airmail M-Bag
    • First-Class Package International Service
    • Priority Mail Express International Flat Rate (Envelopes)
    • First-Class Mail International
    • Priority Mail International Flat Rate
    • International Business Reply Service

Here are several points to consider regarding these USPS services:

  • Fastest delivery speed
    • Domestic Shipments
      • Priority Mail: One to three business days
      • Priority Mail Express: Next- to two-day delivery 
    • International Shipments
      • Global Express Guaranteed: Shipping in one to three business days (one business day to many destinations in Canada)
      • Priority Mail Express International: Shipping in three to five business days 
  • Affordable Options
    • Domestic Shipments
      • USPS Ground Advantage: This service offers low prices for parcels with expected delivery in two to five business days. Prices start at $4.75.
    • International Shipments
      • Priority Mail International: This option ships items weighing over 4lbs in six to ten business days. Prices start at $30.35.
      • First-Class Package International Service: This mailing service ships packages (or large envelopes weighing over 1lb) containing items worth up to $400 and weighing less than 4 lbs.

 USPS Priority Mail

Here are the size, weight, and shape specifications for Priority Mail:

  • The price for mailpieces weighing up to 70lbs going to any U.S. location is the same.
  • When sealing a flat-rate box or envelope, the container flaps must fit within the usual folds.
  • Use Priority Mail Flat Rate boxes or boxes with standard sizes so you don’t need to measure them.

Moreover, here’s the guideline for determining additional fees:

  • Dimensional (DIM) weight charges apply to large, lightweight parcels. 
    Suppose your item is over 1,728 cubic inches (1 cubic foot). In that case, take the following steps:
    • Multiply the parcel’s length, width, and height. 
    • Divide the product by 166 to get the DIM weight in pounds (lbs).
    • If the DIM weight exceeds the package weight, USPS will charge you the DIM weight price.

      Note: If you provide inaccurate dimensions or don’t pay the DIM weight rate (if applicable), you’ll pay a dimension-noncompliance penalty.
  • Nonstandard Fee: You will incur additional costs for sending a nonstandard-size parcel if your package has the following measurements:
    • Add $4 if the package is between 22 to 30 inches long.
    • Add $15 if the package is over 30 inches long.
    • Add $25 if the package is over 3,456 cubic inches (2 cubic feet) in volume.

USPS Priority Mail Express

This service offers money-back guaranteed next-day to two–day delivery by 6:00 PM.

Also, USPS Priority Mail Express has flat-rate envelopes with a set price. You pay the same fee for mailpieces weighing up to 70 lbs sent anywhere in the U.S.

However, note that when securing a Priority Mail Express flat-rate envelope, the container flaps should fit within the regular folds.

Meanwhile, the calculation procedure for additional fees is the same as Priority Mail’s.   

USPS Parcel Select

This option is an affordable ground delivery service for large and medium-sized shipments. Note that size, shape, and weight affect Parcel Select packages.

Suppose your package’s volume exceeds 1,728 cubic inches (1 cubic foot). In that case, the postage will depend on the DIM or actual weight, whichever is greater.

DIM weight pricing applies to Parcel Select Destination Entry packages for all entries.

You may be charged the oversized price rather than the machinable (standard) price if you have a large package.

Also, mailpieces shipped at Parcel Select Destination Entry are charged nonmachinable prices if a parcel must be sorted without using the automated process.

Find the Cheapest Options: USPS First-Class Mail

First-Class Mail is an affordable and convenient way to send envelopes and postcards.

First-Class Mail Forever stamps cost $0.66 (the current 1 oz price) and will never expire, even if the First-Class postage rate goes up.

Latest USPS Shipping Cost and Prices

As of 2023, the shipping costs for domestic shipments by mailing classes are as follows:

USPS ServiceRetail Price (at a post office)Commercial Price
Priority Mail Flat Rate EnvelopeStarts at $9.65 Starts at $8.05
Priority MailStarts at $9.35 Starts at $7.64
Priority Mail ExpressStarts at $28.75Starts at $24.90
Prepaid Forever Priority Mail Flat RateSee pricing hereSee pricing here
Priority Mail Express Open and Distribute  ServiceNot available (N/A)See your USPS sales agent 
Priority Mail Express Flat Rate EnvelopeStarts at $28.75Starts at $24.90
Priority Mail Express ReturnStarts at  $24.90N/A
Priority Mail Return ServiceN/AStarts at $7.64
Priority Mail Open and Distribute ServiceN/AAsk your USPS sales agent
USPS Ground AdvantageStarts at $4.75Starts at $3.59
First-Class MailStarts at $0.66Starts at  $0.498
USPS Ground Advantage ReturnStarts at $4.75Starts at $3.59
Every Door Direct Mail – Retail$0.198 for Flats up to 3.3 ounces (oz)N/A
Parcel SelectN/AStarts at $3.78
USPS Connect LocalStarts at $3.95 online with CNS serviceN/A
USPS Marketing MailN/AStarts at $0.193
Media MailStarts at $3.92Starts at $2.59
Library MailStarts at $3.72Starts at $2.46
USPS Connect Local MailStarts at $2.95 online with CNS serviceN/A
Parcel Select LightweightN/AStarts at $2.46

Meanwhile, the costs for international shipments as of 2023 are as follows:

USPS ServicePost Office PriceCommercial Base PriceCommercial Plus Price




First-Class Mail International
Letters and postcards: Starts at $1.50 for all countries

Large envelopes (flats): Starts at $3.00 for all countries
Priority Mail InternationalStarts at $42.10 Starts at $39.53Starts at $39.53
First-Class Package International ServiceStarts at $15.75Starts at $14.96 Starts at $14.96
Priority Mail Express International Flat Rate (Envelopes)Starts at $54.75 Starts at  $51.98Starts at $51.98
Priority Mail International Flat RateEnvelopes: Starts at $30.35 

Small flat-rate boxes: Starts at  $31.45

Medium flat-rate boxes: Starts at $60.55

Large flat-rate boxes: Starts at $74.00
Envelopes: Starts at $28.57

Small flat-rate boxes: Starts at $29.64

Medium flat-rate boxes: Starts at $56.10

Large flat-rate boxes: Starts at $69.10
Envelopes: Starts at $28.57 

Small flat-rate boxes: Starts at $29.64

Medium flat-rate boxes: Starts at $56.10

Large flat-rate boxes: Starts at $69.10
Priority Mail Express InternationalStarts at $56Starts at $53.07Starts at $53.07
Airmail M-Bag
Starts at $55.00
International Business Reply ServiceStarts at $2.10 per piece

First-Class Mail: Mail-In 1–5 Business Days

First-Class Mail service is a cost-effective and efficient way to mail envelopes and postcards. 

USPS says First-Class mail or packages usually arrive at their intended destinations in one to five business days. 

Features and Pricing

Here are a few points to consider regarding First-Class Mail:

  • This mailing service is the most cost-effective option for items up to 13oz.
  • First-Class Mail is eligible for Delivery Confirmation services, including Certified Mail.
  • First-Class Mail offers one price for up to 3.5oz with commercially priced cards and letters.
  • Prices for First-Class Mail depend on shape and weight.

    Note: A First-Class Mail Forever stamp costs $0.66 (the current 1oz rate) and will never expire, even if the First-Class postage price increases.

Letters

Here are the prices for mailing letters via First-Class Mail:

  • Rectangular, standard-sized envelope stamps begin at $0.66.
  • Square, oversized, or irregularly shaped envelope stamps begin at $1.06.

Postcards

Here are the rates for mailing postcards via First-Class Mail:

  • Rectangular, standard-sized postcard stamps begin at $0.51
  • Stamps for oversized postcards begin at $0.66.

Large Envelopes and Small Packages

The cost of First-Class Mail large envelopes (flats) starts at $1.35. First-Class Mail items beyond a large envelope’s maximum dimensions are classified and priced as a parcel (package).

Weight, Size, and Shape Requirements

First-Class Mail letters must not exceed 3.5oz. On the other hand, a large envelope’s weight must not exceed 13oz.

In addition, flats and postcards must be rectangular. Otherwise, you’ll pay additional postage.

Lastly, additional size restrictions apply to specific types of mailpieces you’re sending.

Additional Charges for Irregular Envelopes, Mailpieces, and Small Packages

Many packages go through the mailing system smoothly. However, irregular shapes or nonstandard specifications can complicate things. These irregularities often incur additional costs.

Nonmachinable Envelopes

Suppose your mail or envelope has an unusual shape like any of the following:

  • Square or vertical
  • Lumpy
  • Rigid
  • With string, clasps, or buttons

USPS’s automated mail processing system will not process your shipment in that case. USPS employees must process it manually (hand-canceled). 

Hand-canceling takes place when a postal worker stamps your package by hand rather than running it through a machine.

For this reason, you might have to pay extra (nonmachinable surcharge) for these types of mail, even if they weigh under 1oz.

Large Mailpieces, Envelopes, and Small Packages

Suppose your sent letter exceeds the First-Class standard envelope maximum height, length, and thickness. In this case, USPS will charge you large envelope (flat) prices.

Additional Information

Say you plan to ship large First-Class envelopes exceeding dimension requirements or are nonrectangular, rigid, or unevenly thick. In this scenario, you will pay package prices, and USPS will ship your envelopes via Ground Advantage.

You can also use USPS’ price calculator to determine postage costs for First-Class Mail shipments. Provide the tool with your mailpiece’s size, shape, and weight information.

Meanwhile, First-Class Package service is more cost-effective for lightweight packages than Parcel Select Ground (formerly Parcel Post) and Priority Mail. 

This option also offers fast delivery across the country in three days or less, comparable to Priority Mail. 

You can ship to any U.S. address and P.O. (post office) box, including the following destinations:

  • FPO (Fleet Post Office) 
  • APO (Army or Air Force Post Office)
  • DPO (Diplomatic Post Office)

Note that free USPS Tracking is available for First-Class Package service.

Mailing Restrictions and Prohibitions

There are specific rules and standards for shipping restricted, prohibited, and HAZMAT (hazardous materials), including cigarettes and smokeless tobacco. You can read the guidelines for these items here.

For Businesses

USPS understands that its businesses want speed, security, affordability, and quality customer service. That’s why USPS offers them discounted services and resources, including the following:

Data-Driven Shipping

You can track (with added services) and measure First-Class Mail items and route them to specific targets, providing multiple business options.

With forwarding and address correction services, your messages will reach a significant portion of your target audience.

Commercial Prices and Automation Discounts

USPS also offers economical prices and discounts:

  • Bulk discounts: First-Class Mail offers commercial rates for presorted letters and flats if you send a minimum of 500 mailpieces. Automation discounts may also apply.
  • One price up to 3.5oz: Pay a single fee for up to 3.5oz for First-Class Mail automation-compatible and presort cards and letters. 

    This fixed pricing is a cost-effective way for businesses to send promotional messages with invoices, bills, and statements. 

    Note: The single rate for up to 3.5oz is not blended and does not include First-Class Mail single-piece letters.

USPS Ground Advantage: Small Packages in 2–5 Business Days

Ground Advantage delivers packages in two to five business days. This service also features USPS Tracking.

Here are additional details regarding this service’s features, ways to purchase and print postage, and other benefits:

  • Ground Advantage is USPS’ best-priced service for items weighing up to 15.999oz, based on weight and zone (distance).
  • This service includes free forwarding, UAA (undeliverable as addressed), and RTS (return to sender) services.
  • Suppose you don’t have a printer. In that case, you can still ship online via the upgraded CNS service. 
    You will pay an extra $1.25 for each label. USPS will then print an outbound label and mail it to you.
  • Ground Advantage packages weighing more than 15.999oz pay by the pound up to 70lbs (rounded up).
  • Pay for Ground Advantage postage through a self-service kiosk, stamps, CNS, or at a post office.
  • Ground Advantage offers no-cost package pickup at your residential or business address.
  • This service is also ideal for shipping HAZMAT, which is only mailable through ground transportation.
  • Ground Advantage includes $100 insurance for both outbound and return shipments.  

Still, you can buy up to $5,000 additional coverage against loss or damage for your goods.

Meanwhile, Ground Advantage pricing tiers are determined by your package’s size, weight, shape, and zone. 

Note that you must use your own packaging and check to ensure it meets the size requirements:

  • Packages up to 15.999oz
    • Price tiers are as follows
      • Up to 4oz 
      • Up to 8oz 
      • Up to 12oz 
      • Up to 15.999oz. 

Note: Round up to the nearest tier. For instance, if your parcel weighs 4.2oz, you’ll pay the 8-oz price.

  • Items that weigh more than 15.999oz are rounded up to 1 pound and are subject to the pound-rate pricing.
  • Large Envelopes (Flats) Being Treated as Packages: You will pay the Ground Advantage price if you send a large First-Class Mail envelope that has the following characteristics:
    • Rigid (cannot bend)
    • Not evenly thick (lumpy)
    • Nonrectangular (square or taller than it is wide)
    • Longer than 11 ½ inches, higher than 6 ⅛ inches, or thicker than ¼ inch
  • Packages weighing more than 15.999oz and up to 70 lbs
    • The maximum weight is 70lbs.
    • For mailpieces heavier than 15.999oz (which rounds up to 1lb), USPS charges by the pound (lb), rounded up. 
      For example, if your parcel weighs 8.3lbs, you will pay the 9lb price.
    • The maximum combined girth and length is 130 inches.

FAQs

  1. How much is each stamp worth?

USPS customers almost always use First-Class Mail when shipping letters, postcards, and larger envelopes.

As of 2023, a 1oz First-Class Mail stamp costs $0.63 if you purchase and print it online through Stamps.com. In contrast, the stamp costs $0.66 at the post office.

Moreover, approved third-party vendors, like Stamps.com, offer postage rate discounts to users who buy stamps online using their services.

Customers usually get discounts through these programs because printing postage online helps reduce congestion at local post offices.

Here are the expected prices and discounts for various mail items sent with Stamps.com postages:  


Mail Item

Max. Weight

Max. Length

Max. Width

Stamps.com Rate

Post Office Rate
Online Postage Discount
Postcard1oz6.0 inches4.5 inches$0.40$0.48$0.03
Letter1oz11.5 inches6.125 inches$0.63$0.66$0.03
Letter2oz11.5 inches6.125 inches$0.81$0.84$0.03
Letter3oz11.5 inches6.125 inches$1.05$1.08$0.03
Letter3.5oz11.5 inches6.125 inches$1.29$1.32$0.03
  1. Does postage go for weight or distance?

The answer to this question depends on the mailing service you purchase.

Your item’s weight determines the postage cost you will pay. Weightier mailpieces are generally more costly than lighter ones.

For example, the cost of shipping via Priority Mail Express depends on the weight and distance your item travels. 

Note: This pricing excludes items mailed using Priority Mail Express Flat Rate packaging.  

Meanwhile, the mailpiece’s weight and shape will determine the price for First-Class Mail shipping.

Distance from the shipping origin also affects the price of mailpieces shipped through specific mail classes. 

The actual distance is grouped in zones. Zones range from zone 1 (local, near you) to zone 9 (very far from you). 

For certain classes of mail, the farther a parcel travels (the more zones it crosses), the higher the postage cost.

Here are four zoned shipping methods:

  • Priority Mail Express
  • Bound Printed Matter
  • USPS Retail Ground
  • Priority Mail

Meanwhile, the following delivery options are not zoned:

  • Library Mail
  • USPS Marketing Mail
  • First-Class Mail
  • Media Mail

You pay a fixed price for each service regardless of your mail’s destination.

  1. What is the best way to send items or parcels weighing less than one pound?

The answer to this question depends on what benefit you want. Suppose you want the most affordable option for shipping parcels weighing under one pound. 

In that case, USPS First-Class Package or Retail Ground may be the best choice since they’re among the cheapest options for shipping parcels weighing less than a pound.

  1. What is the best way to send items or parcels weighing more than one pound?

Again, the answer to this question depends on what you’re looking for in a mailing service.

Some suggest that USPS Ground services like Retail Ground are a good option if you want a cost-effective way to mail large packages or boxes weighing up to 70lbs. 

Still, it is best to verify whether your item complies with USPS’ weight, size, and shape requirements.

Say you’re shipping a parcel weighing over 70lbs. You might consider alternative courier services from FedEx (Federal Express) or UPS (United Parcel Service). 

These shipping companies provide many delivery options for packages weighing over 70lbs. 

  1. How large can an envelope be to be still eligible for First-Class mail letter rates?

A mailpiece is eligible for First-Class Mail letter rates if it has the following dimensions:

  • A minimum width of 3 ½ inches, length of 5 inches, and thickness of 0.007 inches
  • Must not exceed the maximum limit of 6 ⅛ inches (width) by 11 ½  inches (length) by ¼ inch (thickness).

Meanwhile, the maximum size for First Class Mail large envelopes is 15 inches (length) x 12 inches (width) x ¾ inch  (thickness). 

  1. Does USPS charge by size or by weight?

Shipping costs for specific USPS services depend on weight and size. For this reason, USPS recommends using a weighing scale to measure your package’s weight before heading to the local post office.

Suppose you want to estimate your item’s shipping cost based on weight. In that case, you can use USPS’ retail postage calculator. 

Note: Change the unit of measurement in the USPS postage calculator to standard or metric, whichever you prefer.

Here are several crucial points regarding size definitions at USPS:

  • Length always represents the longest dimension and is measured in inches.
  • Width is the side perpendicular to the length and is expressed in inches.
  • Girth is the distance around the thickest area of the non-length sides, measured in inches.
  • Girth is the sum of height multiplied by two and width multiplied by two for rectangular packages.
  • Girth is the circumference of the cylinder for cylindrical containers.
  • Height is perpendicular to the length and is specified in inches.

Note: When calculating the price for a tube-shaped package using the Postage Price Calculator, choose the “Large Package” shape, select the “Nonrectangular” button, and enter the correct dimensions.

  1. What is the biggest box that I can ship with USPS?

The maximum measurement for most mailpieces is 108 inches in combined girth and length. 

Still, USPS Retail Ground items may measure up to 130 inches in combined girth and length (but are subject to oversized prices).

References

1. Parcel Size, Weight & Fee Standards
https://faq.usps.com/s/article/Parcel-Size-Weight-Fee-Standards
2. Weight and Shape/Size
https://postcalc.usps.com/Calculator/ShapeAndSize?country=10013&ccode=AU
3. All About Dimensional Weight Pricing
https://stamps.custhelp.com/app/answers/detail/a_id/6114/~/all-about-dimensional-weight-pricing
4. How to Use the USPS Shipping Calculator
https://www.stamps.com/calculators/how-to-use-usps-shipping-calculator/
5. Click-N-Ship® – The Basics
https://faq.usps.com/s/article/Click-N-Ship-The-Basics
6. Priority Mail
https://www.usps.com/ship/priority-mail.htm
7. Priority Mail Delivery Map
https://www.usps.com/priority-mail/map/
8.Mailing & Shipping Prices
https://www.usps.com/business/prices.htm
9. First-Class Mail Fact Sheet
https://about.usps.com/postal-bulletin/2007/html/pb22218/kit1_010.html
10. USPS First Class Package Service
https://www.stamps.com/usps/first-class-package-service/
11. USPS Ground Advantage
https://www.usps.com/ship/ground-advantage.htm
12. How Weight Affects Prices
https://pe.usps.com/BusinessMail101/Index?ViewName=Weight
13. First-Class Mail Letters
https://about.usps.com/postal-bulletin/2007/html/pb22218/kit1_003.html
14. Minimum and Maximum Sizes
https://pe.usps.com/businessmail101?ViewName=MinMax