USPS Flat Rate Boxes


November 8, 2023

If you ship packages frequently, you understand that calculating shipping costs can be complex, considering that they fluctuate wildly. Various factors influence postage rates, from your chosen delivery service to the distance the parcel must travel.

Weight is among the most critical elements that impact the cost of sending a mailpiece. Generally, the heavier a package, the more expensive it is to deliver. Such can create problems if you’re an individual or business looking to reduce shipping expenses.

However, the United States Postal Service (USPS) changed that in 2004 by introducing flat-rate boxes. In this article, let’s discuss USPS’ convenient and cost-effective offering.

Do you want more information on how much shipping flat-rate boxes will cost? Visit your local post office, which you can easily find using’s USPS facility locator tool.

What Is USPS Priority Mail Flat Rate?

USPS (U.S. Postal Service) Priority Mail Flat Rate is a fantastic shipping option that combines two of USPS’ offerings: its Priority Mail service and Flat-Rate shipping.

 Priority Mail offers 1- to 3-day delivery and flat-rate packaging, which lets you send mail up to 70lbs to all 50 U.S. states for the same price.

How Does USPS Flat Rate Shipping Work?

In a nutshell, USPS Flat Rate shipping is a mail delivery option that lets you choose from various predetermined boxes and envelope sizes appropriate for your mailpiece. USPS will charge you based on your preferred packaging, not the weight or distance it must travel.

Is Priority Mail the Same As Flat Rate?

While Priority Mail and Flat Rate are USPS services that can work together to help you save money on heavy items, they are different. To explain, you can ship packages through USPS Priority Mail and benefit from the 1- to 3-business-day delivery time using your own packaging.

In other words, the standard Priority Mail service lets you forego using flat-rate shipping supplies. However, doing so means your shipping costs must now consider your parcel’s weight and destination.

Which Is Cheaper: Flat Rate or Priority Mail?

While not a hard-and-fast rule, choosing Priority Mail for lightweight items traveling short distances is common. Conversely, using Priority Mail Flat Rate boxes is typically more economical when shipping larger or bulkier items across farther distances.

If you’re mailing a 5lb-package within 150 miles (Zone 2) through Priority Mail, expect to pay $8.95. Using personal packaging in this scenario is cheaper, especially if your mail item requires a medium flat rate box, which costs $14.75.

If you’re sending an item that meets the 70-lb maximum weight limit to a destination that’s over 1,800 miles (Zone 8) from the origin, buying a large flat rate box to ship it will only cost you $19.90. However, if you use your own box, the fee will be $173.27, based on the weight and destination.

When to Use USPS Flat Rate Envelopes

USPS Flat Rate envelopes are an excellent choice for shipping smaller, non-fragile items. Whether it’s important documents, clothing, or small accessories, the content of these envelopes is guaranteed a secure, affordable, and swift delivery.

When to Use USPS Flat Rate Boxes

USPS Flat Rate boxes come in various sizes, making them perfect for shipping items of different dimensions. From the small flat rate box for compact goods like small electronics to the large flat rate box for bulkier items, you’ll find the ideal packaging for your shipments.

Talk to a USPS representative to determine when to use flat-rate packaging or your own. Narrow the list of over 31,000 USPS facilities by visiting and using the post office locator tool.

Is Priority Mail (Weight-Based) or Flat Rate Faster?

Whether you’re shipping a package using a large flat rate box or an old container you had lying around in your home, expect a delivery time through USPS Priority Mail to be between one and three business days.

Benefits of Using Priority Mail Flat Rate With USPS

USPS Priority Mail Flat Rate is the answer if you’re looking for a convenient and cost-effective shipping option. This service has several benefits that make it an excellent choice for individuals and businesses, including the following:

  • Predictable shipping cost: One of the primary upsides of Priority Mail Flat Rate is the fixed shipping cost. This option lets you quickly calculate shipping costs for various products without worrying about the exact weight, dimensions, or destination.
  • Free package pickup: While dropping off a package at a post office is an excellent option to inquire about cost-efficient shipping services, it can be quite a hassle. Fortunately, Priority Mail Flat Rate offers free package pickup, saving you time and effort.
  • Free shipping supplies: Although the size of the flat-rate box determines the cost, USPS provides the container free of charge when you use Priority Mail Flat Rate. You can get these complimentary packaging materials at your local post office or have USPS deliver them to your doorstep.
  • No surcharges: Unlike other shipping options from competitors like FedEx, Priority Mail Flat Rate does not levy additional fees for fuel costs and residential, rural, or weekend deliveries. The flat-rate pricing means no surprises or hidden fees.
  • Simplified packaging and rate calculation: Priority Mail Flat Rate simplifies shipping by offering predetermined box sizes. Choose the appropriate size for your mail item and pay the flat rate. That’s it.
  • Cost-effective for heavy Items: Priority Mail Flat Rate can be cost-effective if you ship heavy mail items over long distances. The fixed pricing lets you send hefty parcels without incurring additional costs based on their weight.

Types of USPS Boxes

USPS offers three different box types to suit your shipping needs. Each box has unique features and benefits, catering to almost every mail item you want to ship.

These boxes include the following:

USPS Flat Rate Boxes

Unlike traditional shipping methods, USPS’ flat-rate options don’t consider a package’s weight, making them a popular choice for shipping heavy items over long distances.

The best part about USPS’ flat-rate packaging options is that you can ship a mail item if it fits into the container and doesn’t exceed the 70-lb weight limit.

Here are your USPS Flat Rate shipping supplies options:

Flat Rate Envelope12 ½” x 9 ½”
Window Flat Rate Envelope10” x 5”
12 ½” x 9 ½”
Small Flat Rate Envelope10” x 6”
Flat Rate Padded Envelope12 ½” x 9 ½”
Legal Flat Rate Envelope15” x 9 ½”
Small Flat Rate Box5 7/16” x 8 11/16” x 1 ¾”
Medium Flat Rate Box (Top-Loading)11 ¼” x 8 ¾” x 6”
Medium Flat Rate Box (Side-Loading)14” x 12” x 3 ½”
Large Flat Rate Boxes12 ¼” x 12 ¼” x 6”
APO (Army Post Office)/FPO (Fleet Post Office)/DPO (Diplomatic Post Office) Flat Rate Box12 ¼” x 12 ¼” x 6”
Large Flat Rate Board Game Box24 1/16” x 11 ⅞” x 3 ⅛”

USPS Regional Rate Boxes

As of January 22, 2023, USPS has discontinued the Regional Rate Box pricing. Nonetheless, the USPS Regional Rate Boxes service was an excellent option for shipping small shipments over short distances, as the package’s outer dimensions dictate the pricing rather than its weight.

Here are the Regional Rate Boxes USPS used to offer:

Regional Rate Box A1 (Top-Loading)10 ⅛” x 7 ⅛” x 5”
Regional Rate Box A2 (Top-Loading)13 ⅙” x 11 1/16” x 2 ½”
Regional Rate Box B1 (Top-Loading)12 ¼” x 10 ½” x 5 ½”
Regional Rate Box B2 (Top-Loading)15” x 12” x 3”

USPS Forever Prepaid Flat Rate Boxes

Like USPS Flat Rate Boxes, the Forever Prepaid Flat Rate Boxes option lets you send items to any U.S. destination for a fixed price, as these containers include postage.

The unique feature of forever prepaid boxes is their prices are tied to Forever Stamps and don’t have an expiration date. Hence, these boxes are a reliable option for long-term shipping needs and could hedge against future price increases.

The available box sizes for Forever Prepaid Flat Rate include the following:

Priority Mail Forever Prepaid Flat Rate Envelope12 ½” x 9 ½”
Priority Mail Forever Prepaid Legal Flat Rate Envelope15” x 9 ½”
Priority Mail Forever Prepaid Padded Flat Rate Envelope12 ½” x 9 ½”
Priority Mail Forever Prepaid Small Flat Rate Box5 7/16” x 8 11/16” x 1 ¾”
Priority Mail Forever Prepaid Medium Flat Rate Box (Top-Loading)11 ¼” x 8 ¾” x 6”
Priority Mail Forever Prepaid Medium Flat Rate Box (Side-Loading)14 ⅛” x 12” x 3 ½”
Priority Mail Forever Prepaid Large Flat Rate Box12 ¼” x 12” 6”

Do USPS Flat Rate Shipments Come With a Tracking Number?

As part of the Priority Mail service, flat-rate shipments automatically come with USPS tracking. Using USPS’ tracking tool, you can monitor your parcel’s progress throughout its journey.

How Do I Get a USPS Priority Mail Flat Rate Label?

Obtaining a Priority Mail Flat Rate label is a breeze with USPS’ Click-N-Ship application. Whether a residential customer or a small business owner, you can use this tool to create postage labels online for an additional $1.25 surcharge.

Alternatively, you can get a USPS Priority Mail Flat Rate label by visiting your local post office. Find your area’s most convenient postal service facilities using’s USPS locator tool and database.

Overview and Description of Available Priority Mail Flat Rate Boxes and Envelopes

As mentioned, USPS offers various flat-rate packing options to suit your shipping needs. While we briefly touched on these options earlier, let’s discuss them further.

USPS Priority Mail Flat Rate Small Box

For small items large enough to fit in envelopes, such as small electronic gadgets or books, the Small Flat Rate Box option is the ideal flat-rate packaging choice. This container comes in dimensions of 8 11/16” x 5 7/16” x 1 ¾” and costs $8.55.

USPS Priority Mail Flat Rate Medium Box

USPS’ Medium Flat Rate Boxes have two variations: top- and side-loading, with dimensions of 11 ¼” x 8 ¾” x 6” and 14” x 12” x 3 ½”, respectively. Choose these boxes if you send clothing, accessories, and office goods. Shipping with a medium flat rate box costs $14.75.

USPS Priority Mail Flat Rate Large Box

The Large Flat Rate Box service is ideal for shipping bulkier items like full-sized computers and large household items. The measurements of the sizeable flat-rate packaging variant are 12 ¼” x 12 ¼” x 6”. It costs $19.90 to ship.

USPS Priority Mail Flat Rate Envelopes

If you’re shipping essential documents, tickets, or jewelry, you have several USPS Priority Mail Flat Rate Envelopes to choose from, including the following:

USPS Priority Mail Flat Rate Envelope12 ½” x 9 ½”$8.05
USPS Priority Mail Legal Flat Rate Envelope15” x 9 ½”$8.35
USPS Priority Mail Padded Flat Rate Envelope12 ½” x 9 ½”$8.80

USPS Priority Mail APO/FPO/DPO Large Flat Rate Box

The APO/FPO/DPO large flat rate box is specially designed to house mail items headed for military and diplomatic post offices.

USPS Flat Rate Box SizesAPO/FPO/DPO

The dimensions for an APO/FPO/DPO large flat rate box are 12 ¼” x 12 ¼” x 6”. It costs $18.35.

Features and Pricing

USPS flat rate boxes are known for their competitive pricing and excellent features. Here are some frequently asked questions:

How Much Does USPS Charge for Flat Rate Boxes?

The pricing for USPS flat rate boxes varies based on your chosen box size. For instance, USPS will charge $8.55 for a small flat rate box and $19.90 for a large-sized container, regardless of where you’ll send it in the U.S.

What Is the Postage Cost for USPS Envelopes?

Unlike other USPS shipping services like First-Class Mail, Flat Rate Envelope postage pricing varies on the envelope size, not the weight. Expect a price of around $8.05 to $8.80, depending on the envelope type.

Use USPS Priority Mail Packaging and Pay a Flat Rate

As mentioned, when you opt for USPS Priority Mail Flat Rate packaging, you benefit from the simplicity of paying one fixed price for mailpieces weighing up to 70lbs. This flat-rate pricing applies regardless of the parcel’s destination within the U.S.

Use Your Own Box and Pay by Weight and Zone (Distance)

Alternatively, USPS provides a weight- and zone-based pricing system if you prefer to use your own box for shipping. With this option, your package’s weight and travel distance determine the shipping cost.

However, USPS may charge additional fees for sending non-standard box sizes. For example, you must pay $4 for a parcel between 22” and 30” long, while you’ll be charged $25 if your mailpiece exceeds two cubic feet.

Why USPS Medium and Large Flat Rate Boxes Might Not Be for You

While medium and large Priority Mail Flat Rate boxes are excellent eCommerce shipping solutions, they have drawbacks that may not suit some delivery situations.

For one, shipping medium and large boxes can be more expensive than using alternative shipping classes or your own packaging, especially for shorter distances. 

Additionally, because USPS’ flat-rate services use fixed-sized boxes, there may be better choices for packages with specific weights and shapes. You must consider other shipping options if your items don’t fit well within these fixed-size boxes.

How Do I Pay for the Postage of a Priority Mail Flat Rate Box?

You can pay for the postage of your Priority Mail Flat Rate box using various methods, including printing your shipping label online with USPS’ Click-N-Ship application. You can also visit your local post office, which you can find using’s facility locator tool.

Are There Any Pickup Options Available for a Priority Mail Flat Rate Box?

Through the Package Pickup online notification, you can inform your local post office that you have a Priority Mail Flat Rate mailpiece they must collect. The advantage of this option is that it’s free.

For even more flexibility, you can opt for the Pickup on Demand service, available for an additional fee. It allows you to schedule a specific time for USPS to collect your parcel.

What Extra Services Are Available With the Priority Mail Flat Rate Box?

Using the Priority Mail Flat Rate Box service, you also receive insurance coverage up to $100, apart from the free tracking and pickup. However, you can also purchase additional benefits, including the following:

  • Certified Mail: With Certified Mail, you get proof of mailing and delivery and the recipient’s signature upon delivery. This service is perfect for essential documents or sensitive items that require verification.
  • Registered Mail: For maximum security, you can choose Registered Mail, which offers the highest level of protection for valuable and irreplaceable items. This service also includes restricted handling, ensuring only the recipient can accept the package.
  • Signature Confirmation: By opting for Signature Confirmation, you can ensure that your Priority Mail Flat Rate Box reaches your intended recipient by obtaining the receiver’s signature upon delivery.
  • Collect on Delivery (COD): If you conduct business transactions that involve payment upon delivery, you can use COD services. This option allows the recipient to pay when they receive the package.
  • Additional Insurance: While the Priority Mail Flat Rate service includes insurance coverage up to $100, you can buy additional insurance of up to $5,000 for more protection.

Mailing Restrictions and Prohibitions

You must follow U.S. and USPS guidelines while you can ship items if they fit inside a flat-rate box. Some mail items are prohibited, while others are restricted and subject to specific conditions, such as limiting transportation to ground vehicles.

For more information on mailing restrictions, contact USPS customer service at 1-800-ASK-USPS (1-800-275-8777) or visit your local post office. Find your area’s nearest USPS facilities using’s postal service finder tool.


  1. What do I do with unused USPS boxes?

You can reuse, recycle, or return unused USPS boxes to your local post office.

  1. How do I track a free USPS box?

You can monitor your free USPS boxes using your shipment’s tracking number via USPS’ tracking tool.

  1. How can I get free USPS boxes?

You can order free USPS boxes online at the USPS website at, and USPS will deliver the shipping supplies to your doorstep at no cost. Alternatively, you can receive them at a nearby post office.

  1. What is USPS Regional Rate shipping?

The USPS Regional Rate shipping option worked similarly to the USPS Flat Rate service in that pricing considered the package’s dimensions instead of its weight. However, this service is now unavailable.

  1. Should you use your own box for a custom size?

If your item doesn’t fit into USPS’ flat-rate packaging, you can use your own boxes and opt for standard Priority Mail. Unfortunately, the shipping cost will now consider the parcel’s weight and travel distance.