Calculate USPS Priority Mail Cubic Pricing

We offer incredible discounts with USPS Priority Mail Cubic. Since these rates are based on the size of the package, not the weight, use this calculator to find out what you'll pay. Remember! Cubic is only available for domestic packages:
  • Weighing less than 20 lbs.
  • With a cubic foot value up to 0.5.
  • With each side measuring 18 in. or less

USPS Cubic TIer Calculator

Your Dimensions Are Too Big For Cubic Tier
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Your Dimensions Are Too Big For Cubic Tier
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What Should I Charge For Shipping?

Cubic pricing simplifies shipping charges, because anything that fits in the box—up to 20 pounds—will ship for the same price, just depending on the Zone.

Here are our tips for choosing the best shipping price to charge your customers.

Variable, Zone-based Pricing

If you want your customers to cover the exact cost of shipping, you’ll need to set up rules in your checkout flow to show the proper rate based on the Zone. See here for a USPS domestic zone chart.


0-150 miles
150-300 miles
Zone 3
300-600 miles
Zone 4
600-1000 miles
Zone 5
1000-1400 miles
Zone 6
1400-1800 miles
Zone 7
1800+ miles
Zone 8
Zone 9

Fixed Shipping Pricing

If you’d like to charge a fixed rate, here are your options.*

Lowest Possible Rating

The Average Rate

The Full Monty

Charge all customers the cheapest rate in your rate table, and then you must cover the difference, if any.
Choose a shipping price that’s the average of all of the prices in your rate table.
Charge all customers the most-expensive rate, and then if you pay less, you can pocket the difference.

* These rates do not include Zone 9, the Zone reserved for shipping to U.S. territories. These rates are strictly for the contiguous U.S., Hawaii, and Alaska.

Should I Use a Flat Rate Box Or My Own Packaging?

Any items small enough to fit in the USPS Priority Mail Flat Rate or Regional Rate packaging are also small enough to qualify for Cubic pricing.

We did the math to determine when you should use your own packaging (and ship Priority Mail Cubic) and when you should grab a Flat or Regional Rate box.

Here are the USPS-branded boxes that fit your Cubic Tier and when you should use them.

Your Own Packaging x Flat or Regional Rate Package
2022 Cubic Tier 0.1 - USPS Small Flat Rate Box (8 11/16” x 5 7/16” x 1 ¾”)
Weight Zone
Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Zone 9
0.5 lbs $7.16 $7.46 $7.67 $7.88 $7.90 $7.90 $7.90 $7.90
1 lbs $7.16 $7.46 $7.67 $7.88 $7.90 $7.90 $7.90 $7.90
2 lbs $7.32 $7.59 $7.81 $7.90 $7.90 $7.90 $7.90 $7.90
3 lbs $7.32 $7.59 $7.81 $7.90 $7.90 $7.90 $7.90 $7.90
4 lbs $7.32 $7.59 $7.81 $7.90 $7.90 $7.90 $7.90 $7.90
5 lbs $7.32 $7.59 $7.81 $7.90 $7.90 $7.90 $7.90 $7.90
6 lbs $7.32 $7.59 $7.81 $7.90 $7.90 $7.90 $7.90 $7.90
7 lbs $7.32 $7.59 $7.81 $7.90 $7.90 $7.90 $7.90 $7.90
8-20 lbs $7.32 $7.59 $7.81 $7.90 $7.90 $7.90 $7.90 $7.90
21-70 lbs $7.90 $7.90 $7.90 $7.90 $7.90 $7.90 $7.90 $7.90

How Do I Get Cubic Pricing In Shippo?

USPS Priority Mail Cubic is instantly available to all Shippo customers at signup—no volume threshold required.


We promise you’ll always be shown the best rates during your label creation flow, including USPS Priority Mail Cubic, if your box qualifies. Make sure to select Enter Custom Dimensions or choose a qualifying Package Template when entering package details.

Cubic prices will be listed as USPS Priority Mail. Once you print your label, you’ll see Cubic in the top right corner of your label under the postage box:

Envelopes and Poly Mailers (also known as Soft Pack)

To access Soft Pack pricing, select Carrier Provided Parcels* in the Package section. Scroll through the drop down and select Soft Pack. Enter the package details and the Cubic rate will load as USPS Priority Mail.

*Note: you must use your own envelope or poly mailer to qualify. Do not use a USPS-branded package.

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