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).

Service
Transit Time
Max Dimensions (inches)
Max Weight (ounces)
First
1-5 business days
Cards, Letters and Flats only (no Parcels)See Predefined Packages (Card, Letter, Flat) for details
13
Priority
1-3 business days
Combined Length and Girth < 108in
1120
Express
1-2 days
Combined Length and Girth < 108in
1120
GroundAdvantage
2-5 days
Combined Length and Girth < 130in
70
LibraryMail
2-8 business days
Combined Length and Girth < 108in
1120
MediaMail
2-8 business days
Combined Length and Girth < 108in
1120
FirstClassMailInternational
Must be rectangular, otherwise an additional charge may apply.
15.994
FirstClassPackageInternationalService
7-21 days
Packages (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 restrictions
64
PriorityMailInternational
6-10 business days
Combined Length and Girth < 108in
1120
ExpressMailInternational
3-5 business days
Combined Length and Girth < 108in
1120

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)
Card
6in x 4.5in x 0.016in
NA
Letter
11.5in x 6.125in x 0.25in
NA
Flat
11.5in x 6.125in x 0.75in
NA
FlatRateEnvelope
12.5in x 9.5in
NA
FlatRateLegalEnvelope
15in x 9.5in
NA
FlatRatePaddedEnvelope
12.5in x 9.5in
NA
FlatRateWindowEnvelope
10in x 5in
12.5in x 9.5in
NA
FlatRateCardboardEnvelope
12.5in x 9.5in
NA
SmallFlatRateEnvelope
10in x 6in
NA
Parcel
Varies based on service level
NA
SoftPack
Varies based on service level
320
SmallFlatRateBox
8.6875in x 5.4375in x 1.75in
NA
MediumFlatRateBox
11.25in x 8.75in x 6in
14.125in x 12in x 3.5in
NA
LargeFlatRateBox
12.25in x 12in x 6in
NA
LargeFlatRateBoxAPOFPO
12.25in x 12.25in x 6in
NA
FlatTubTrayBox
NA
EMMTrayBox
NA
FullTrayBox
NA
HalfTrayBox
NA
PMODSack
NA

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.

String
Description
AIR_ELIGIBLE_ETHANOL
Air Eligible Ethanol Package
CLASS_1
Class 1 - Toy Propellant/Safety Fuse Package
CLASS_3
Class 3 - Package
CLASS_7
Class 7 - Radioactive Materials Package
CLASS_8_CORROSIVE
Class 8 - Corrosive Materials Package
CLASS_8_WET_BATTERY
Class 8 - Nonspillable Wet Battery Package
CLASS_9_NEW_LITHIUM_INDIVIDUAL
Class 9 - Lithium Battery Marked - Ground Only Package
CLASS_9_USED_LITHIUM
Class 9 - Lithium Battery - Returns Package
CLASS_9_NEW_LITHIUM_DEVICE
Class 9 - Lithium batteries, marked package
CLASS_9_DRY_ICE
Class 9 - Dry Ice Package
CLASS_9_UNMARKED_LITHIUM
Class 9 - Lithium batteries, unmarked package
CLASS_9_MAGNETIZED
Class 9 - Magnetized Materials Package
DIVISION_4_1
Division 4.1 - Mailable flammable solids and Safety Matches Package
DIVISION_5_1
Division 5.1 - Oxidizers Package
DIVISION_5_2
Organic Peroxides Package
DIVISION_6_1
Division 6.1 - Toxic Materials Package (with an LD50 of 50 mg/kg or less)
DIVISION_6_2
Division 6.2
EXCEPTED_QUANTITY_PROVISION
Excepted Quantity Provision Package
GROUND_ONLY
Ground Only
ID8000
ID8000 Consumer Commodity Package
LIGHTERS
Lighters Package
LIMITED_QUANTITY
Limited Quantity Ground Package
SMALL_QUANTITY_PROVISION
Small 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 Label
USPS 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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