USPS Flat Rate Envelope


June 26, 2023

Calculating shipping costs, choosing appropriate packaging, and ensuring timely delivery can be complex and time-consuming. For any e-commerce or retail business to flourish, finding a convenient and cost-effective shipping solution is critical. 

Enter USPS Flat Rate envelopes, a shipping option for businesses that handle high volumes of packages. They simplify the shipping process while helping manage costs by eliminating the need for intricate weight, dimension, and pricing calculations.

Whether you’re operating a business or simply need to send essential items, you’ll want to keep reading. In this article, we dive into USPS Flat Rate Envelopes and how they can be a reliable and hassle-free shipping option.

Speaking of hassle-free, the USPS has over 31,000 facilities in the U.S. Finding one near you that offers shipping options that fit your needs and can help optimize your business shipping can also take time. Visit to simplify this process.

What Are USPS Flat Rate Envelopes?

USPS Flat Rate envelopes are a convenient and cost-effective shipping option that the United States Postal Service (USPS) provides. In a nutshell, they’re packaging that allows you to ship items at a “flat rate” or a fixed fee, regardless of the weight or destination.

Using USPS Flat Rate envelopes can streamline your shipping process and save you money. With a predetermined fee, you eliminate the need to manage your package contents’ weight and calculate postage – perfect if you regularly ship heavy packages over long distances.

How Does USPS Flat Rate Shipping Work?

Businesses that frequently send items of different sizes and weights may find the process of shipping packages to be problematic. Flat Rate shipping solves this problem by letting you fit as many mailpieces as possible in a container up to a specific weight limit.

But how does USPS Flat Rate shipping work? Here’s a quick breakdown:

  • You choose your packaging: While you no longer need to consider the number of items you’re sending, you still need the right-sized container to put them in. USPS offers several options for weight limits, envelopes, and box sizes.
  • Pack your package: Next, you put the items into the appropriate Flat Rate packaging. You can put as many things as your Flat Rate envelope or box can handle, as long as the weight doesn’t exceed their limits.
  • Pay the fixed fee: Regardless of the weight, dimension, or destination of your package, Flat Rate shipping will charge you, as the name suggests, a predetermined fee. This fixed cost removes the need for complicated calculations.
  • Bid your package farewell: Once you’ve securely packed your items and paid the flat rate, all that’s left is to wait for your shipment to arrive at your intended destination. Domestic Priority Mail Flat Rate shipping generally takes one to three business days.

Is Priority Mail the Same As Flat Rate?

While Priority Mail and Flat Rate are shipping options USPS offers, they differ in pricing and packaging structure.

Priority Mail refers to USPS’s fast and reliable shipping service, which offers various packaging options based on weight and size. Unlike Flat Rate shipping, Priority Mail fees consider the shipping destination.

On the other hand, Flat Rate shipping involves using specific envelopes and boxes provided by USPS at a predetermined flat rate, regardless of weight or destination.

What Is Priority Mail Flat Rate?

Priority Mail Flat Rate is a Priority Mail shipping service with a Flat Rate feature. It allows you to ship Flat Rate envelopes with the benefits of USPS Priority Mail, such as one to three-day delivery and free home or office pickup, at a fixed price, regardless of weight or destination.

Priority Mail Flat Rate shipping gives you a convenient and cost-effective option for shipping heavier items and longer distances, which generally results in higher costs with traditional shipping services.

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

Priority Mail Flat Rate shipping gives you a one- to three-day delivery time. However, Priority Mail Express boasts one of the fastest shipping times of one to two days, shaving a day off.

Which Is Cheaper: Flat Rate or Priority Mail?

Whether Flat Rate or weight-based Priority Mail is cheaper depends on various factors, including your package’s weight, size, and how far it’s going.

Flat Rate shipping is particularly advantageous if you regularly send heavy items over long distances, as the flat fee remains the same regardless of the package’s weight.

However, weight-based Priority Mail options may give you a more cost-effective solution when shipping lighter packages across shorter distances.

When to Use USPS Flat Rate Envelopes

USPS Flat Rate envelopes are an intelligent choice if you’re a business looking for a fast, cost-effective shipping solution. 

  • Cost savings: You pay a fixed fee with Flat Rate shipping. In contrast, other shipping services will factor your package’s weight and its destination into the shipping cost.
  • Expedited delivery: USPS Flat Rate envelopes ensure quick delivery, typically within one to three business days. This fast turnaround time allows you to meet customer expectations and increase customer satisfaction.
  • Package consolidation: You can combine multiple items into a single package without worrying about increased costs. Doing so lets you streamline your shipping process and improve efficiency.

What Priority Mail Flat Rate Envelopes Are Available?

USPS offers a variety of Priority Mail Flat Rate envelopes to suit different shipping needs. Here are some commonly available Priority Mail Flat Rate envelopes:

Priority Mail Flat Rate EnvelopesSizeFeatures
Priority Mail Flat Rate envelope12½” x 9½”Quick, easy, and convenientPredetermined rate regardless of weight or destinationIdeal for various documents and lightweight items
Priority Mail Window Flat Rate envelope10″ x 5″ or 12½” x 9½”Smaller version: Window for pre-addressed envelopes, #10 size or smallerLarger version: Accommodates full-page documents and large pre-addressed envelopes
Priority Mail Small Flat Rate envelope10″ x 6″Convenient for folded documents, letters, cards, and small items like passports
Priority Mail Padded Flat Rate envelope12½” x 9½”Lined with bubble padding for added protection
Priority Mail Legal Flat Rate envelope15″ x 9½”Perfect for legal-size documents at a low flat rate

Priority Mail Window Flat Rate Envelope

Here’s what you need to know about Priority Mail Window Flat Rate envelopes:


The Priority Mail Window Flat Rate envelope is a convenient mailing solution with a transparent window allowing easy viewing of the contents. It’s designed explicitly for shipping documents, letters, and other flat items securely and efficiently.

Product Specs

The envelope has dimensions of 10 inches by 5 inches (with the flap closed). It can accommodate items up to the maximum weight allowed for Flat Rate envelopes.

Shipping Info

When shipping your packages using the Priority Mail Window Flat Rate envelope, you can drop them off at your local post office or schedule a pickup for added convenience. These shipments come with additional services such as insurance coverage and USPS Tracking.

Priority Mail Small Flat Rate Envelope

Here’s what you need to know about Priority Mail Small Flat Rate envelopes:


The Priority Mail Small Flat Rate envelope is a compact and efficient solution for sending folded documents, letters, cards, and other small items. This envelope type provides convenient Priority Mail Flat Rate shipping, ensuring quick and reliable delivery.

Product Specs

This envelope measures 10 inches by 6 inches (with the flap closed), offering ample space for small documents such as letters, cards, and other similar items.

Shipping Info

USPS offers free standard shipping with Parcel Select service within two to five business days and expedited shipping with Priority Mail service for a fee, guaranteeing delivery within one to three business days.

Priority Mail Padded Flat Rate Envelope

Here’s what you need to know about Priority Mail Padded Flat Rate envelopes:


The Priority Mail Padded Flat Rate envelope is a reliable choice for shipping items at a flat rate while providing additional protection. It’s designed with bubble padding lining to safeguard the contents during transit, ensuring they reach their destination intact.

Product Specs

This padded envelope has dimensions of 12-1/2 inches (L) x 9-1/2 inches (W). It offers ample space to accommodate various items while providing cushioning with its bubble padding lining.

Shipping Info

To ship using the Priority Mail Padded Flat Rate envelope, you can order packs of 10 envelopes from the Postal Store website. The Postal Store does not accept international shipments but does ship to APO/FPO/DPO addresses and U.S. territories.

APO stands for Army Post Office, FPO is for Fleet Post Office, and DPO for Diplomatic Post Office. Members of the respective branch of service work in these post offices. 

Priority Mail Legal Flat Rate Envelope

Here’s what you need to know about Priority Mail Legal Flat Rate envelopes:


The Priority Mail Legal Flat Rate envelope is the perfect solution for swiftly delivering legal-size documents while enjoying the benefits of a low flat rate. It offers a cost-effective and efficient shipping option for legal materials.

Product Specs

This envelope has dimensions of 15 inches (L) x 9-1/2 inches (H), providing ample space to accommodate legal-size documents securely.

Shipping Info

To utilize the Priority Mail Legal Flat Rate envelope, you can order packages of 10 envelopes from the Postal Store website. You can track your shipment with USPS Tracking service, with one business day for processing and shipping.

What Is the Postage Cost for USPS Flat Rate Envelopes?

Flat Rate pricing varies on the USPS Flat Rate envelope type and whether it’s for commercial base or post office pricing.

Envelope TypeCommercial PricePost Office Price
Flat Rate envelope$8.05$9.65
Window Flat Rate envelope$8.05$9.65
Small Flat Rate envelope$8.05$9.65
Padded Flat Rate envelope$8.80$10.40
Legal Flat Rate envelope$8.30$9.95
Small Flat Rate box$8.55$10.20
Medium Flat Rate box (top-loading)$14.75$17.10
Medium Flat Rate box (side-loading)$14.75$17.10
Large Flat Rate box$19.90$22.80
APO/FPO/DPO Large FRB$18.35$21.20

The prices above are subject to change. You can visit USPS’s official website at if you need additional information. 

Alternatively, you can ask your local post office agent about Flat Rate envelope pricing. You can use’s facility locator tool to find the nearest post office.

Use USPS Priority Mail Packaging and Pay a Flat Rate:

Take advantage of USPS Priority Mail Flat Rate packaging when shipping your items. Doing so allows you to pay a single price regardless of weight for shipments within the U.S., eliminating the need for measuring.

Mailing Restrictions & Prohibitions

You must follow U.S. and USPS guidelines when sending letters or packages through Flat Rate shipping. Some items are completely prohibited, while others are restricted and subject to specific conditions, such as limiting transportation to ground vehicles.

Shipping to a Military Post Office (APO/FPO/DPO)

Shipping to military addresses through APO/FPO/DPO offers USPS special provisions and services. These exclusive offers include domestic pricing for USPS Flat Rate boxes you send to overseas military post offices.

You also receive access to free military shipping kits, addressing tips, and country-specific guidance on mailing restrictions and allowances. USPS assists with customs forms, including detailed package descriptions for EU countries.

For Businesses

If you’re a business that frequently sends packages, you understand the significance of a speedy, affordable, and secure mail service. USPS recognizes these priorities and offers various services and resources that meet your business goals and needs.

Priority Mail Open & Distribute

You can streamline the transportation of your bulk mailings with Priority Mail Open and Distribute (PMOD). This service expedites the delivery of your items by shipping them in USPS-approved containers to authorized locations.

PMOD also distributes the contents of your packages to their final destinations. PMOD allows you to take advantage of commercial rates based on weight and zone. At the same time, it ensures the prompt delivery of your parcels while keeping costs reasonable.

Can You Put Anything in a USPS Flat Rate Envelope?

According to USPS, as long as an item fits in the Flat Rate envelope, the product ships, no matter how much it weighs or how far it’s going. However, as mentioned previously, there are items you cannot send through USPS.

These items include:

  • Airbags
  • Ammunition
  • Explosives
  • Gasoline
  • Marijuana (medical or otherwise)
  • Intoxicating liquors
  • Firearms
  • Knives and sharp instruments
  • Liquids, powders, and odor-producing materials
  • Motor vehicle master keys
  • Obscene materials
  • Poison
  • Switchblade knives
  • Tobacco products
  • Used hypodermic needles and syringes
  • Aerosols
  • Cigarettes and tobacco
  • Dry ice
  • Firearms
  • Lithium-ion batteries
  • Live animals
  • Nail polish
  • Perfumes (containing alcohol)
  • Prescription drugs
  • Sharp instruments
  • Some types of alcohol
  • Some types of batteries
  • Some types of plants and seeds

For a comprehensive list of prohibited and restricted items, you can refer to USPS’s shipping prohibitions and restrictions page. You can also consult your local post office for detailed information on mailing regulations and requirements.

 Contact post offices in your area using’s extensive facility database and locator tool.

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

If you’re a business that frequently sends packages, obtaining a USPS Priority Mail Flat Rate label is essential to take advantage of the benefits of the service. Fortunately, getting a Priority Mail Flat Rate label is simple and convenient.

  • Order shipping supplies: You can order USPS-branded Flat Rate packaging, including envelopes and boxes, from a local USPS facility or through the USPS online store.
  • Print a label online: Another convenient way to obtain a USPS Priority Mail Flat Rate label is by purchasing and printing it online. Some online postage providers can give you discounted rates for doing so.
  • Visit a post office: You can visit a post office to purchase and print a Priority Mail Flat Rate label. You can also visit to find the nearest facility and engage with USPS staff directly, allowing you to address all your questions while getting the necessary Flat Rate branding.

USPS Will No Longer Let You Do This, Effective Immediately

On January 24, 2021, USPS discontinued one of its Flat Rate options, the Priority Mail Prepaid Flat Rate Stamped envelope, offered since 2003.

The USPS Has Gotten Rid of One of Its Flat Rate Envelopes

USPS no longer allows its customers to purchase Priority Mail Prepaid Flat Rate Stamped envelopes. The deadline for you to use these envelopes was until January 2022. If you unfortunately still have them, you can no longer utilize them for shipping.

The Agency Says Demand for This Shipping Option Has Declined

USPS decided to discontinue the Priority Mail Prepaid Flat Rate Stamped envelopes based on declining orders and rising production and fulfillment costs.

Certain USPS Products Have Recently Gotten Smaller As Well

Unfortunately, USPS’s removal of the Priority Mail Prepaid Flat Rate Stamped envelopes can affect your shipping options, as it has also reduced the sizes of some of its shipping products by as much as a quarter of an inch.

The Postal Service Also Recently Updated Its Prices for Several Products

USPS implemented several price changes following the removal of the Flat Rate service. The prices for Priority Mail and Express services increased by approximately 3.1%. Fortunately, there was a reduction in fees for Large Flat Rate boxes.

Understanding these changes allows you to plan and adjust your business solutions. 

Check out USPS’s website to stay informed, or visit a post office in person. You can use’s post office locator tool to find the most convenient facility in in California, Texas, Florida, Illinois, Michigan, and other states.


  1. USPS Priority Mail
  2. A Guide on When and Why to Use USPS Flat Rate Boxes and Envelopes
  3. What Priority Mail Flat Rate® Envelopes Are Available?
  4. Priority Mail Flat Rate Window Envelope
  5. Priority Mail Flat Rate Small Envelope
  6. Priority Mail Flat Rate Padded Envelope
  7. Priority Mail Flat Rate Legal Envelope
  8. USPS Parcel Select
  9. USPS Military & Diplomatic Mail
  10. USPS Flat Rate Package Options
  11. USPS Priority Mail Flat Rate
  12. USPS Will No Longer Let You Do This, Effective Immediately
  13. Discontinuance of the Priority Mail Pre-Paid Flat Rate Stamped Envelope