The USPS support website provides many helpful resources, including refund and insurance claim information, and other frequently asked questions.
- Length — the longest edge of a package
- Width — the second longest edge of a package
- Height — the shortest edge of a package
- Girth — (2 x width) + (2 x height)
Domestic Weight and Dimensional Limits
|Service||Weight Limit||Dimensional Limit|
|First-Class Mail||13 oz||Minimum: 6 in x ¼ in x 3 in (L x W x H)
Maximum: 27 in x 17 in x 17 in (L x W x H)
|Priority Mail, Priority Mail Express, Media Mail, Library Mail||70 lbs||Maximum length plus girth must not exceed 108 in|
|Standard Post, Parcel Select||Maximum length plus girth must not exceed 130 in|
International Weight and Dimensional Limits
USPS’s website provides a Customer’s Guide to Mailing, which has helpful tips on packing and shipping best practices, and even offers free shipping supplies, including boxes, that they will ship to your home or business.
Service Specifics and Rate Calculation
The Postal Service provides a comparison of services on their site, which can help you decide which services are the best fit for you, your product and your customers. Standard Post and Media Mail are not available for international shipping. Generally, for shipments under 6 ounces, First-Class Mail offers the lowest cost solution.
There are several factors that can affect what a shipment will cost:
USPS Real Time Quotes Common Issues
Symptom: Returned quotes on the storefront don’t match what is displayed on the USPS postage calculator.
- If you’re using our older USPS integration, and Package size is not set to “Large”, package dimensions aren’t submitted when requesting a quotes, so if the package has a larger dimensional weight than the actual weight, the returned quote will be too low.
- Physical dimensions aren't defined for the product. Some real-time shipping providers require these in order to provide your customers with an accurate shipping quote during checkout. Typically, the narrowest dimension should be set as the factoring dimension in your physical dimension settings.
Symptom: Certain services completely fail to return a quote.
- The package might be exceeding the limits for that service. For example, if your product weighs 4 ounces, and a shopper adds 4 of them to the cart, the combined weight is 16 ounces, and would not qualify for First-Class Mail.