USPS Ship USPS Flat Rate Boxes with EasyPost

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What are USPS Flat Rate Boxes?

USPS Flat Rate Boxes are just that — boxes with flat postage rates, no matter how heavy the package is. If you're shipping heavy, small items, Flat Rate Boxes can be one of the cheapest ways to ship, since the shipping cost remains the same regardless of the package weight or shipping distance. Keeping a supply of these boxes on hand for your fulfillment operations can cut your shipping costs by 50% annually.

USPS offers a variety of flat rate packaging options, including 6 sizes of envelopes and 4 types of boxes, to fit your unique shipping needs. All supplies are free of charge and can be picked up at your local Postal Office or mailed to you directly through USPS's website.

All Flat Rate packages are supported through the EasyPost Shipping API by using predefined packages, so it's easy to set up internally and start collecting savings from your Flat Rate Boxes as soon as you integrate with EasyPost.

How Much Does Shipping For USPS Flat Rate Boxes Cost?

EasyPost offers USPS Commercial Plus Pricing, making flat rate boxes a cost effective option for shipping. See our rate chart below for details.

USPS Priority Mail Flat Rate Options

Last Updated: January 26, 2020.

TypeSizeEasyPost Predefined PackagePrice
Letter Envelope12 1/2" x 9 1/2"FlatRateEnvelope$7.15
Gift Card Envelopes10" x 7"FlatRateGiftCardEnvelope$7.15
Window Envelopes10" x 6"FlatRateWindowEnvelope$7.15
Small Envelopes10" x 6"SmallFlatRateEnvelope$7.15
Padded Envelopes12 1/2" x 9 1/2"FlatRatePaddedEnvelope$7.75
Legal Envelopes15" x 9 1/2"FlatRateLegalEnvelope$7.45
Small Box8 11/16" x 5 7/16" x 1 3/4"SmallFlatRateBox$7.65
Medium Boxes11 1/4" x 8 3/4" x 6" or 14" x 12" x 3 1/2"MediumFlatRateBox$13.20
Large Box12-1/4" x 12-1/4" x 6" or 24-1/16" x 11-7/8" x 3-1/8"LargeFlatRateBox$18.30
APO/FPO Box12-1/4" x 12-1/4" x 6"LargeFlatRateBoxAPOFPO$16.80

Note: Rates are ESTIMATED. When you purchase postage, these rates may differ.

If you have any questions about our Commercial Plus pricing use the button below to contact us.

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