(Note: The rates in the video above are out of date, but the concept remains the same 😉 see below for the current rates!)
USPS Priority Mail Medium Flat Rate Boxes and Large Flat Rate Boxes are specific types of packaging that you can get from a Post Office or USPS.com/supplies.
How to Use Flat Rate Packaging: To ship these boxes, you have to buy the corresponding kind of Flat Rate postage by specifying the exact type of packaging you're shipping when you're creating a label.
Flat Rate May Not Be the Cheapest Option: Flat Rate labels are convenient since you don't need to worry about the size or weight of the box... but if you're sending lightweight items, Flat Rate may be more expensive than other USPS services like Priority Mail Cubic or USPS Ground Advantage.
Examples of when Priority Mail Medium & Large Flat Rate Boxes are more expensive than other USPS services
If your items weigh less than 20 lbs, Medium and Large Flat Rate Boxes can be much more expensive than using your own packaging and shipping with Priority Mail Cubic instead.
Here are some examples that illustrate how Flat Rate Packaging can be more expensive:
The Priority Mail Medium Flat Rate Box comes in two sizes:
Medium Flat Rate Box 1 Dimensions: 11 x 8.5 x 5.5 inches
Medium Flat Rate Box 2 Dimensions: 14 x 12 x 3.5 inches
If you used your own box that was the same size or even a little bigger, like 14 x 12 x 4 inches, it would be in the 0.4 cubic feet pricing tier of Priority Mail Cubic and can save you up to $6.94, depending on how far you're shipping it.
See the image below to see a savings comparison between the Medium Flat Rate Box and Priority Mail Cubic:
Note that for the furthest distances, the Medium Flat Rate Box can be a better deal than Priority Mail Cubic
Some packaging alternatives instead of the Medium Flat Rate Box
As alternatives to the Priority Mail Medium Flat Rate Box, you can use your own custom-sized box or other Priority Mail packaging that qualifies for cubic rates. We've listed those below.
USPS Mailing Boxes: USPS offers two free "mailing boxes" in the cubic 0.4 size:
Priority Mail Box - 1095 | 15-1/4" x 12-3/8" x 3" | Cubic Tier 4
Priority Mail Box - Shoe Box | 7-1/2" x 5-1/8" x 14-3/8" | Cubic Tier 4
Non-USPS Packaging: You can save even more if you use a custom box that's small enough to fit into the 0.3 cubic feet pricing tier of Priority Mail Cubic. See a rate comparison here.
The Priority Mail Large Flat Rate Box comes in one size:
Large Flat Rate Box Dimensions: 12 x 12 x 5.75 inches
If you used your own box that was the same size or even slightly larger, like 12 x 12 x 6 inches, it would be in the 0.5 cubic feet pricing tier of Priority Mail Cubic and can save you up to $8.66, depending on how far you're shipping it.
See the below image for a savings comparison:
Note that for the very furthest distances, the Large Flat Rate Box does offer some savings over Priority Mail Cubic.
Save More With Custom Packaging: You can save even more if your own box is small enough to fit into the 0.4 cubic feet pricing tier of Priority Mail Cubic. You can see a rate comparison here.
Related Resources