Bonus! Determine if a USPS Flat Rate box is the cheapest option for the items you’re looking to ship, since it’s not always the most affordable choice.

Sign up for a free Shippo account to access the best rates on USPS Flat Rate shipping and print your labels from the comfort of your office or home.

You have to use the branded Flat Rate boxes to get the Flat Rate shipping price, and you can order them online or pick them up at your local Post Office. Order free Flat Rate boxes from the USPS.To ship with this service, follow these easy steps: The USPS Priority Mail Flat Rate service will ship your package anywhere in the U.S. You can easily ship like the experts just know the USPS Flat Rate box sizes, prices, and how it works before you buy. That is the exact cubic dimension of your package.USPS Priority Mail Flat Rate boxes are an easy-to-use, cost-effective shipping option. Multiply the Length, Width, and Height, and then divide that total by 1,728. For boxes that aren't square, measure the Length, Width, and Height of your box in inches. A 2 cubic foot square box is pretty big and well beyond the size of most packages being shipped. A square package 2 feet by 2 feet is 2 Cubic feet. A square package 1 foot by 1 foot is 1 cubic foot. *Calculating the cubic dimensions of your packages isn't difficult. And when shipping packages, select Large Package. We suggest reviewing your shipping process to ship in the smallest box possible to avoid these surcharges.

If the volume of the package is greater than 2 cubic feet, a $15.00 surcharge will be applied*.If the longest side of a package is greater than 30 inches, a $7.00 surcharge will be applied.Packages with missing or incorrect package dimensions that result in any dimensions-based fees, a $1.50 surcharge will be applied.If the volume of the package is greater than 2 cubic feet, a $25.00 surcharge will be applied*.

If the longest side of a package is greater than 30 inches, a $15.00 surcharge will be applied.

If the longest side of a package is more than 22 inches but less than 30 inches, a $4.00 surcharge will be applied.

USPS Priority Mail and Priority Mail Express

Padded flat rate envelope sizes