USPS Package Restrictions

If you need to know how big your USPS parcel can be, we have all the numbers you need below

What size and weight restrictions does USPS have?

The Predefined Package names are drawn from the EasyPost API, so you can better reference how each Predefined Package matches up dimensionally.

Predefined Package Name	Dimensions	Weight
Card	Min: Min: Domestic: 5" x 3 ½" x 0.007" International: 5 ½" x 3 ½" x 0.007" Max: 6" x 4 ¼" x 0.016"	Must be a flat surface
Letter	Min: Domestic: 5" x 3 ½" x 0.007" International: 5 ½" x 3 ½" x 0.007" Max: 11 ½" x 6 ⅛" x ¼"	Maximum weight is 3.5 oz.
Flat	Min: 11 ½" x 6 ⅛" x ¼" (must exceed one of these dimensions) Max: 15" x 12" x 3/4"	Maximum weight is 13 oz.
Parcel	Domestic: Maximum size for USPS Ground Advantage is 130" in combined length and girth (distance around the thickest part). Other mail classes maximum size is 130" in combined length and girth. International: Maximum length + height + thickness combined = 36 inches	Maximum weight is 70 lbs.
FlatRateEnvelope	12 ½" x 9 ½"	Domestic maximum weight is 70 lbs. International maximum weight is 4 lbs.
FlatRateLegalEnvelope	15" x 9 ½"	Domestic maximum weight is 70 lbs. International maximum weight is 4 lbs.
FlatRatePaddedEnvelope	12 ½" x 9 ½"	Domestic maximum weight is 70 lbs. International maximum weight is 4 lbs.
FlatRateGiftCardEnvelope	10" x 7"	Domestic maximum weight is 70 lbs. International maximum weight is 4 lbs.
FlatRateWindowEnvelope	10" x 5"	Domestic maximum weight is 70 lbs. International maximum weight is 4 lbs.
FlatRateCardboardEnvelope	12 ½" x 9 ½"	Domestic maximum weight is 70 lbs. International maximum weight is 4 lbs.
SmallFlatRateEnvelope	12 ½" x 9 ½"	Domestic maximum weight is 70 lbs. International maximum weight is 4 lbs.
SmallFlatRateBox	8 ⅝" x 5 ⅜" x 1 ⅝"	Maximum weight is 70 lbs.
MediumFlatRateBox	11" x 8 ½" x 5 ½"	Maximum weight is 70 lbs.
LargeFlatRateBox	12" x 12" x 5 ½"	Maximum weight is 70 lbs.
SoftPack	The longest dimension may not exceed 18 inches. Cubic rating will be applied using Length and Width only. See more details on the USPS Cubic Pricing page.	Maximum weight is 20 lbs.

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