How to Save Money on USPS Shipping

For e-commerce sellers, USPS (the United States Postal Service) is still one of the most ubiquitous options for shipping their wares to customers. Sellers are always looking for the latest trick in how to save money on USPS shipping, and I wrote this post in hopes of creating the ultimate guide, combining all the different options one can save a few bucks.

Why Use USPS for Shipping?

The United States Postal Service covers the entire United States and its territories (Puerto Rico, Guam, U.S. Virgin Islands, etc.) for generally the same rates. Whereas, other carriers like UPS and FedEx will have significantly different pricing in some cases (stay tuned; toward the end of the article, you’ll see just exactly how insane the pricing differences can be).

Related: The 5 Best E-commerce shipping services compared and when you should use each of them.

(Editor’s Note: The prices in this article were correct as of June 2019 and based on the USPS’ 2019 rates. They have since been raised so plan accordingly.)

USPS has three major service tiers that dictate its offerings:

  1. First-Class
  2. Priority Mail
  3. Parcel

Within those three major tiers, the services can be broken down further:

  1. First-Class Letter (for letters and documents)
  2. First-Class Package (1 to 16 oz)
  3. Priority Mail (16oz or more–the typical USPS service)
  4. Priority Mail Cubic
  5. Priority Mail Flat Rate (package size tiers for a single price, regardless of the weight)
  6. Priority Mail Express (overnight and 2-day shipping version of Priority Mail Flat Rate)
  7. Parcel Select Ground (the slowest of the services–up to 7 days–and doesn’t have commercial discounts as valuable as the other services)

For e-commerce sellers, First-Class Package and Priority Mail will be where most focus their effort. For some that have heavy objects that can fit in specific Flat Rate boxes, the Priority Mail Flat Rate service might be a better deal, though delivery times will not be any quicker. Flat Rate appears to be tailored to general retail customers looking to ship their wares without paying the insane retail rates.

For the continental United States, Priority Mail and Priority Mail Flat Rate is delivered in 1-3 business days. Priority Mail Express is in 1-2 days.

Parcel Select Ground should be avoided as it is as expensive if not more expensive than the other services in a lot of scenarios and can take up to a full 7 days to deliver to a location. Priority Mail with the suggestions below will be much faster and cheaper.

How to Save Money on USPS Shipping

Man prepares box that would be an ideal example for how to save money on USPS shipping
If this person wants to save money on shipping, that box would be an ideal candidate for USPS Priority Mail Cubic.

It’s no secret that retail rates can look like highway robbery. USPS’ commercial rates are meant to promote using the service in higher volume, so USPS is willing to cut down their pricing a bit to bring in that coveted volume. Now that we have an idea of the options available, let’s go over how we can save money on these services.

Leverage Commercial Discounts with a Shipping Service

All the big-name shipping services offer USPS shipping prices at the commercial level. For those looking to save money on USPS shipping, this is the way to do it.

Some might be cheaper than others still, in that it’s common to either make a small profit on the shipping (add a few pennies) or offer a monthly service fee. Behind the scenes, a shipping service can work out a Negotiated Services Agreement with the USPS that can include special negotiating and pricing that allows the shipping service to collect fees or kickbacks for USPS to make rock-bottom pricing feasible.

Cubic Rates = Big Discounts

This is a pricing offer you won’t see offered on the USPS website or at the post office but is an offering that can absolutely help save money on USPS shipping. Cubic promotes small, dense offerings, with up to 20 lb packages crossing the country for less than $7.

BONUS: How to get a free thermal label printer and shipping labels.

In order to ship Cubic, the package has to be less than 0.5 cubic feet in volume. To figure out the cubic volume, add the three dimensions (length, width, height) and divide by 1728. Round the final value up to the next one-tenth (0.24 rounds up to 0.3).

Example: A cube package of 8 inches in each dimension multiples up to 512 cubic inches. Converting that to cubic feet (divide by 1728), ends up at 0.29 cubic feet. Rounding up places this package in the 0.3 tier.

The math:

8 x 8 x 8 = 512

512 / 1728 = 0.29 => 0.3

Priority Mail Cubic’s pricing is based on the cubic volume tier (0.1 – 0.5) and zone (Zone 1 to Zone 9). The Zone is determined based on the distance in which a package has to travel.

Go Even Further With a Poly/Bubble Mailer

If your item can fit in a poly mailer or a bubble mailer, it’s possible to go even further still in your quest to save money on USPS shipping. The Cubic Softpack dimension rules take effect with a poly mailer, potentially leading to even better pricing. Like regular Cubic, Cubic Softpack has the same five-tier system but uses max length-width dimensions instead. (Height isn’t considered, here.)

TierLength (in) + Width (in) Range
0.1 ft30.01 to 21″
0.2 ft321.01 to 27″
0.3 ft327.01 to 31″
0.4 ft331.01 to 34″
0.5 ft334.01 to 36″

The most astute may notice the dimensions get pretty large. Because of this, if you can fit your box that’s too large for regular cubic into a poly or bubble mailer, you might be able to take Cubic pricing, anyway, saving big on shipping.

Example: A 13 x 13 x 6 package is too large for Cubic on its own, but it can potentially fit into a 24″ poly mailer pouch and end up getting 0.2 ft3 pricing.

If this sounds familiar, it should. You might have heard others in the e-commerce space, especially on YouTube, call this “box in a bag.” Getting a $.60 poly mailer at Staples can save you 10x its cost in shipping charges, if not more. Not convinced? Check out this next section.

Cubic Price Comparisons

Here are a few examples of how to save money on USPS shipping when using cubic versus regular Priority Mail, UPS Ground, or FedEx Ground (bold is cheapest):

Package SizeCubicSoftpackPriority MailUPScFedExc
8x8x8, 3 lbs
Zone 3a
8x8x8, 3 lbs
Zone 8b
12x12x6, 8 lbs
Zone 3
12x12x6, 8 lbs
Zone 8

a 150-300 miles distance, (for UPS & FedEx: Seattle, WA to Salem, OR)
b 1800+ miles, on-continent, (for UPS & FedEx: Seattle, WA to Franklinville, NJ)
c Retail, Ground

USPS Shipping to U.S. Territories

Other services like UPS and FedEx can charge a literal arm and a leg for the privilege of shipping packages to the U.S. Territories. This is where the USPS can really shine in some circumstances. U.S. Territories fall under Priority Mail as they’re considered Domestic destinations. Here’s how the savings can break down. In this example, I’ve used packages that fit in all five Cubic tiers:

12x12x6, 8 lbs
Zone 9

d Seattle, WA to Yigo, Guam (ZIP 96929)

How to Ship Cubic with USPS

Most of, if not all the popular shipping services will offer USPS Cubic shipping as an option. You won’t likely ever see this as a retail offering at and may or may not have luck getting this rate at the local post office.

My favorite service is Pirate Ship for straight USPS shipping, and Sendle if you’re more into having a positive effect on the world with your shipping partner. Others like Shippo, ShipStation, etc. should also support this. Just look for the Priority Mail Cubic option when choosing your shipping service and speed.


It’s not uncommon for folks to see USPS retail rates and be turned off by the service, but for those looking to save money on USPS shipping, utilizing Cubic can be the difference between having a healthy margin and none at all.

Unless someone requests specific shipping (two-day, next-day, overnight, etc.) the USPS’ shipping options can be amazing values for the money. Packages greater than 20 lbs aren’t good for Priority Mail or Cubic, and UPS Ground or FedEx Ground would likely be better options, but for e-commerce sellers who sell smaller items, it’s hard to find a better price for shipping.


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