If you own an ecommerce business, you’ve probably had someone tell you Priority Mail flat rate shipping is the only way to go.
You’ve also probably had people tell you flat rate shipping is a scam.
Our friends over at Essential Hub have shared some great insight on how to navigate shipping.
Here’s the honest truth straight from our shipping experts: there is not a universally “right” way to ship a package. The right solution will vary by box size, package weight, and final destination.
What is flat rate shipping?
Most people who talk about flat rate shipping are talking about Priority Mail Flat Rate, but that is only one type of USPS flat rate shipping USPS (the other two are Priority Mail Regional Rate and Priority Mail Cubic).
Each of these “flat” rate services uses the same network to provide the same services (tracking, insurance, guaranteed delivery window, etc.), but the pricing structure varies based on package weight, size, and destination.
Priority Mail Flat Rate—designed to simplify shipping large, heavy packages that need to travel long distances, Priority Mail Flat Rate charges a flat fee for any package under 70 pounds that can fit into a free flat rate box.
Priority Mail Regional Rate—similar to Priority Mail Flat Rate, Priority Mail Regional Rate is perfect for medium-sized packages between 15–20 pounds that don’t have to travel too far to reach their final destination.
Priority Mail Cubic Rate—best for small, heavy packages, Priority Mail Cubic charges a flat shipping rate, calculated by delivery zone, for packages that weigh less than 20 pounds and have dimensions smaller than 18” for the longest side (basically the size of a shoebox).
| Priority Mail Flat Rate | Priority Mail Regional Rate | Priority Mail Cubic Rate | |
| Package Size | Whatever can fits into a flat rate box | Medium-sized but still what fits into a flat rate box | Small packages no bigger than .5 cubic feet |
| Package Weight | Up to 70 pounds | 15–20 pounds | Up to 20 pounds |
| Package Destination | Long distances | Short-range shipping | Rates change by zone |
For the purposes of this article, we are going to lump Priority Mail Flat Rate and Priority Mail Regional Rate together and compare them against USPS Priority Mail Cubic.
USPS Priority Mail flat rate vs. USPS Priority Mail Cubic
One of the biggest advantages of USPS flat rate shipping is that shippers don’t need to weigh their packages or buy their own boxes. For ecommerce companies that self-fulfill orders, those two benefits alone deliver much-needed time savings.
USPS Priority Mail Flat rate also has three boxes ranging from small to large, which gives merchants affordable options for multiple package sizes. The standard pricing model of Priority Mail flat rate allows ecommerce businesses to accurately estimate their monthly or quarterly shipping costs.
The problem is that even if your shipping estimates are accurate, if you aren’t careful, Priority Mail flat rate will cost you more than you need to pay. If you aren’t filling that flat rate box to the brim, or if you’re not shipping something all the way across the country, regional or cubic rates could save you anywhere from $1–$4 a package.
Which means those free boxes aren’t really free at all.
USPS Priority Cubic doesn’t provide free boxes, but it does deliver significantly better rates than Priority Mail flat rate for small, heavy packages.
Priority Cubic is kind of a hidden secret in the shipping world, partially because this program is only available to companies that ship over 50,000 packages a year (small and mid-sized ecommerce companies can get around this requirement by using a shipping aggregator like Essential Hub).
Depending on where you’re shipping, Priority Cubic can save you anywhere from $7–$123 per package over Priority Mail flat rate prices for small, heavy items. With savings like that, it doesn’t matter that Priority Cubic doesn’t provide free boxes. You can design and produce amazing packaging branded with your company logo and still save money on shipping.