USPS Rates in ShipStation

Explanation of USPS rates available to ShipStation users via Stamps or other USPS postage providers. Includes description of rate types and Stamps rate tables.

The USPS rates available in ShipStation will reflect the rates available to your connected postage provider accounts (, Endicia), including any negotiated rates enabled for that account.

By default, ShipStation users with a account have access to discounted USPS pricing corresponding with Commercial Base pricing. These rates will automatically apply to shipments when using any service valid for the shipment.

This article provides further details on how USPS rates apply in ShipStation.

Types of USPS Rates

The USPS uses a tiered-rate system. This table outlines each rating tier, and what it means.

Rate Tier



The non-discounted rate you pay in person at the post office.

Commercial Base Pricing (CBP)

Online rates through (slightly discounted from retail)

Commercial Plus Pricing (CPP)

Highly-discounted rates available to high-volume shippers (must meet a minimum annual shipment threshold)

Cubic Pricing

Highly-discounted rates for high-volume shippers for packages under 20lbs that are no larger than .5 cubic feet (must meet a minimum annual shipment threshold)

Negotiated Rates

If you have a negotiated service contract with your USPS postage provider (, Endicia, etc), these rates will automatically be available in ShipStation. Rates in ShipStation

Through ShipStation’s relationship with, you automatically have access to the following rates in ShipStation:

Commercial Base Pricing (CBP) rates for these services:

  • Domestic: First Class Package Service, Priority Mail and Priority Mail Express (flat rate and weight-based services)

  • International: Priority Mail International, Priority Mail Express International, and First Class Mail International Package Service

For more information on other discounts your account might be eligible for, please contact your account manager.

Review each section below for rate information on specific domestic service classes.

Check Weight and Dimensions

To avoid rate adjustments, ensure that you are using appropriate dimensions and weight for the service. Postage providers may change weight and dimension requirements for service classes at any time.

Visit USPS Mail Classes Comparison for the most updated information.

Priority Mail Packages/Thick Envelope

Priority Mail packages or thick envelopes are a great way to quickly, yet efficiently, ship packages that are under 70 lbs and do not exceed 108" in combined length and girth (girth = the distance around its thickest part).

Incorrect dimensions or oversized packages with sides that exceed 20" or 30", or over 2 cubic feet, are subject to the USPS Nonstandard Fee and Dimensional Noncompliance Fee.

For information on cubic pricing for packages under 20 lbs and 0.5 cubic feet, please contact your account representative directly.

Priority Flat Rate

Priority Mail Flat Rate is a 1-3 day shipping service that charges one flat rate for your package/envelope, with a maximum allowable weight of 70 lbs. 

Priority Regional Rate Boxes

Priority Regional Rate Boxes have a zone-dependent flat rate. Depending on the zone you are shipping to, you may find the Regional Rate Box is cheaper. Essentially, Flat Rate Boxes are ideal for shipping long distances and Regional Rate Boxes are ideal for shorter distances.

Below are the costs of sending Regional Rate Boxes to each of the USPS's 9 zones. 

Regional Rate Box A: 10" x 7" x 4.75"

Regional Rate Box B: 12" x 10.25" x 5"

To view zones relative to your ship from location, use the USPS Domestic Zone Chart tool

First Class Mail Package

If your package weighs less than 16oz and does not exceed 22" length x 18" width x 15" height (USPS measurement guide), it qualifies for First Class Mail.

First Class Mail rate are based on both weight and zone.

Other USPS Postage Providers

Other USPS postage providers, like Endicia, will offer access to CBP rates as well as an option for negotiated rate contracts. To find out what rates are available for which services from these postage providers, please contact them directly.

The rates available through your postage provider accounts will automatically be available to you in ShipStation!