There are some pretty simple rules of thumb when it comes to knowing what will be the cheapest way to ship with USPS. This quick guide covers the basics of what you need to know 😊
The cheapest USPS services for your shipment
The cheapest way to ship with USPS depends on the type of package you're sending, or how fast you want it delivered.
15.9 ounces or less: If your package is 15.9 ounces or less, then using your own packaging with USPS Ground Advantage service will always be the cheapest option.
Small & over 1 lb: If your package is over 1 pound but it fits into any Flat Rate Envelope or the Small Flat Rate Box, those are the cheapest ways to go.
Over 1 pound but not small: If your package is over 1 pound and doesn't fit into those, then it's cheapest to use USPS Ground Advantage, as long as you're okay with a 2-5 day delivery speed.
Cheapest fast service: If you need a faster service, use as small of a box as possible to qualify for Priority Mail Cubic.
Avoid Flat Rate boxes: Only if your package weighs more than 20 pounds or you're shipping to the farthest zones and it weighs more than 2-3 pounds would Medium or Large Flat Rate Boxes ever be a good deal.
Use free Priority Mail packing to lower costs
One benefit of Priority Mail Cubic is you can use your own packaging, but USPS also offers free boxes you can use with Priority Mail Cubic. We've listed those below, along with their outer dimensions ("OD") and which cubic pricing tier they belong to:
Priority Mail Box - 1096L | OD: 9-7/16" x 6-7/16" x 2-3/16" | Cubic Tier 1
Priority Mail Box - 4 | OD: 7-1/4" x 7-1/4" x 6-1/2" | Cubic Tier 2
Priority Mail Box - 1097 | OD: 11.625" x 2.5" x 13.4375" | Cubic Tier 3
Priority Mail Box - 1092 | OD: 12.25" x 2.875" x 13.6875" | Cubic Tier 3
Priority Mail Box - 1095 | OD: 12.5" x 3.125 x 15.375" | Cubic Tier 4
Priority Mail Box - Shoe Box | OD: 7-3/8" x 5-1/4" x 14-7/8" | Cubic Tier 4