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USPS Guide

This guide will teach you what makes USPS different from other carriers.

The goal of this guide is to detail the best and cheapest ways to use United States Postal Service (USPS) shipping. From the best ways to offer returns to the USPS competitive pricing, we will walk you through predefined packages, service levels, labels structures, and pick-up guidelines.

USPS has multiple service levels to support your business' every need. Naturally, the price of shipping packages increases as the delivery time decreases. EasyPost supports all of USPS' functionality, along with the full functionality of 100+ other carriers.

If you haven't shipped your first label with EasyPost, we recommend you check out our Getting Started Guide.

USPS Pricing

There are two USPS pricing tiers: Retail and Commercial.

EasyPost offers the lowest cost tier for all of our customers. Just sign up and get started shipping with Commercial Pricing.

EasyPost also supports Cubic Pricing. Cubic Pricing is based on the volume, in cubic feet, of a package. Cubic feet can be calculated for rectangular packages by using the following equation: Length x Width x Height / 1728. Cubic feet can be calculated for soft packages by using the Length and Width, and looking up the sum in the Soft Pack pricing tier table. Cubic Pricing allows EasyPost customers to spend less on small, dense packages.

Service Levels

USPS has several service levels supported by EasyPost. Service levels have to do with both the speed and type of shipments. Each service level is detailed below. For reference, Girth is 2 times (Width + Height).

Transit Time
Max Dimensions (inches)
Max Weight (ounces)
First1-5 business daysCards, Letters and Flats only (no Parcels)See Predefined Packages (Card, Letter, Flat) for details13
Priority1-3 business daysCombined Length and Girth < 108in1120
Express1-2 daysCombined Length and Girth < 108in1120
GroundAdvantage2-5 daysCombined Length and Girth < 130in70
LibraryMail2-8 business daysCombined Length and Girth < 108in1120
MediaMail2-8 business daysCombined Length and Girth < 108in1120
FirstClassMailInternationalMust be rectangular, otherwise an additional charge may apply.15.994
FirstClassPackageInternationalService7-21 daysPackages (Other Than Rolls): Combined Length and Girth < 108inRolls (Tubes): Length: min 4in; max 36 in. Length plus twice the diameter (combined): min 6.75 in; max 42in.Some countries have specific prohibitions and restrictions64
PriorityMailInternational6-10 business daysCombined Length and Girth < 108in1120
ExpressMailInternational3-5 business daysCombined Length and Girth < 108in1120

Predefined Packages

USPS has several predefined packages supported by EasyPost, linked below. Predefined packages are an easy way to classify and therefore price a package. With the EasyPost API, pick a predefined package that qualifies for your shipment (and sometimes add the weight) in your request and request rates. See sample request in our predefined package documentation.

Predefined Package
Dimensions (inches)
Weight (ounces)
6in x 4.5in x 0.016in
11.5in x 6.125in x 0.25in
11.5in x 6.125in x 0.75in
12.5in x 9.5in
15in x 9.5in
12.5in x 9.5in
10in x 5in
12.5in x 9.5in
12.5in x 9.5in
10in x 6in
Varies based on service level
Varies based on service level
8.6875in x 5.4375in x 1.75in
11.25in x 8.75in x 6in
14.125in x 12in x 3.5in
12.25in x 12in x 6in
12.25in x 12.25in x 6in

Hazardous Materials (HazMat)

According to USPS, HazMat is any article or substance designated by the U.S. Department of Transportation as being capable of posing an unreasonable risk to health, safety, or property during transportation. In international commerce, HazMat is known as "dangerous goods." HazMat items include but are not limited to explosives, flammable and combustible materials, and radioactive materials. Interestingly, many electronic devices with lithium batteries are HazMat according to USPS. If you're unsure whether your shipment contains HazMat,USPS provides a helpful table of HazMat items on their website.

These are some of the key properties of HazMat shipments. More details can be found in USPS Pub 52.

  • Extra services are restricted to only adult signature or USPS Insurance.

  • Refunds for domestic Priority Mail Express are not be available for shipments containing HazMat if the item is delivered or delivery was attempted within three days of the date of mailing. This is because they may require different handling than those that do not contain HazMat.

  • Shipping labels for HAZMAT packages will have additional content including the following (see the image below of a sample HAZMAT label):

    • a service indicator "H" for identification
    • the words "HAZMAT - Surface Transportation Only" below the return address for surface-only packages
    • the word "HAZMAT" after "USPS TRACKING #" above the tracking barcode.
USPS HazMat Label
  • Some HazMat types are restricted from aircraft and will only return available ground rates.
  • Shippers are responsible for other required HAZMAT markings and documentation for packaging.
  • EasyPost will upload HAZMAT type electronic data to USPS.

Due to the complexity of HazMat regulations and how each carrier handles them differently, many HazMat types are limited to specific carriers. Therefore, to get rates from multiple carrier you will need to make a separate rate request using each carrier's specific HazMat identification type. Selecting a HazMat type supported by another carrier not listed below will result in no USPS rates returned.

The table below shows valid string values and descriptions of each HazMat type supported by USPS. Refer to USPS Pub 52 Hazardous Material and Dangerous Goods regulations.

AIR_ELIGIBLE_ETHANOLAir Eligible Ethanol Package
CLASS_1Class 1 - Toy Propellant/Safety Fuse Package
CLASS_3Class 3 - Package
CLASS_7Class 7 - Radioactive Materials Package
CLASS_8_CORROSIVEClass 8 - Corrosive Materials Package
CLASS_8_WET_BATTERYClass 8 - Nonspillable Wet Battery Package
CLASS_9_NEW_LITHIUM_INDIVIDUALClass 9 - Lithium Battery Marked - Ground Only Package
CLASS_9_USED_LITHIUMClass 9 - Lithium Battery - Returns Package
CLASS_9_NEW_LITHIUM_DEVICEClass 9 - Lithium batteries, marked package
CLASS_9_DRY_ICEClass 9 - Dry Ice Package
CLASS_9_UNMARKED_LITHIUMClass 9 - Lithium batteries, unmarked package
CLASS_9_MAGNETIZEDClass 9 - Magnetized Materials Package
DIVISION_4_1Division 4.1 - Mailable flammable solids and Safety Matches Package
DIVISION_5_1Division 5.1 - Oxidizers Package
DIVISION_5_2Organic Peroxides Package
DIVISION_6_1Division 6.1 - Toxic Materials Package (with an LD50 of 50 mg/kg or less)
DIVISION_6_2Division 6.2
EXCEPTED_QUANTITY_PROVISIONExcepted Quantity Provision Package
ID8000ID8000 Consumer Commodity Package
LIGHTERSLighters Package
LIMITED_QUANTITYLimited Quantity Ground Package
SMALL_QUANTITY_PROVISIONSmall Quantity Provision Package

USPS Labels

EasyPost supports both domestic and international USPS labels in the following format: PNG, PDF, ZPL, EPL2, and ASCII. Request or convert your file type of your labels using our Label API. Below are two test PNG Labels, one is an international label (left) and the other is a domestic label (right):

USPS International LabelUSPS Domestic Label

USPS Pickups

USPS will pick up your package for free if you have one of following package types out for shipment:

  • Priority Mail Express
  • Priority Mail
  • Ground Advantage
  • USPS Returns
  • International

Requests must be received by 2:00 AM CST in order to be picked up that day. After 2:00 AM CST, the USPS will pick up your packages during the next business day. Packages must be properly sealed and ready for shipment.

Need More Info About USPS?

Our Carrier Metadata endpoint can programatically return information about USPS including service levels, predefined packages, supported features, and shipment options.

Use this information to quickly integrate with USPS or make educated decisions about your carrier mix. You can also use the Carrier Metadata endpoint to retrieve information about all the carriers on the EasyPost platform.

Talk to a Shipping Expert

Any questions about how to start shipping with USPS through the EasyPost API?

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