USPS Priority Mail - Domestic Service and Package Rates | Guide

USPS Priority Mail is one of the most popular shipping services among eCommerce merchants - and for good reason. It is reasonably priced, gets your products delivered fast, comes with insurance protection, and offers a variety of discounted packages and service options. Learn more about the features of USPS Priority Mail.

When coupled with commercial discounts, not only are the savings extensive but so are the shipping options. It seems like a great problem to have until you are faced with selecting which USPS Priority Mail service to use.

This guide will help frequent shippers optimize shipping services.
If you ship infrequently, check out our top picks for the cheapest USPS services.

Overview of USPS Priority Mail Service Options

Domestic USPS Priority Mail rates are available through four pricing options:

  • Weight-based
  • Flat Rate packages (boxes and envelopes)
  • Regional Rate boxes
  • Dimensional-based

Most shippers are very familiar with weight-based and Flat Rate package options. However, there are many situations in which Regional Rate boxes and dimensional-based rates will yield lower rates.

In the end, it all comes down to a few key factors:

  1. Weight of the package
  2. Size of the product, which determines the size of the package
  3. The distance the shipment has to travel, which determines the Zone of the shipment

Questions to Evaluate USPS Priority Mail Options

This guide will help you find the most cost-effective USPS Priority Mail service for you. To make the most of it, take some time to work through these questions:

What is the average weight of your packages?

ShippingEasy helps you extract this information with the Shipping Destinations Report. Learn about the Shipping Destinations Report.

What are the package sizes that you use most often? 

Consider if your packages fit into Flat Rate packages or Regional Rate boxes.

Use our USPS domestic package guide to evaluate which USPS boxes fit your products.

If you use custom packages, calculate the volume of those packages to determine if they qualify for Flat Rate Green. Most packages with a volume of less than 0.50 cubic feet will qualify.

Use this formula to calculate your package dimensions for Flat Rate Green:

[ Length x Width x Height ] / 1728 = Cubic Feet

Where do you ship most of your shipments?

USPS uses Zones to determine shipping distance. Learn more about Zones.

ShippingEasy helps you deduct this information on the REPORTS page. Learn about the REPORTS dashboard.

Strategy to Evaluate USPS Priority Mail Options

Once you have created a profile for your shipments, using the questions above, use this table to determine which services your packages qualify for:

  Max Weight Max Dimensions
Weight-rates 70 lbs Max girth 108"
Flat Rate packages
70 lbs Must fit in branded packaging
Regional Rate boxes 20 lbs Must fit in branded packaging
(Flat Rate Green)
20 lbs Less than 0.50 cubic feet
All sides less than 18 inches

Now that you know which services your packages qualify for, use these guides to compare your options and find the services that provide the best value for your business. Start by finding the section for the service(s) that you currently use, then click through the bullets to see how it compares with alternative services:

Weight-based versus:
Flat Rate packages versus:
Regional Rate boxes versus:
Dimensional-based (Flat Rate Green) versus:


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