USPS

USPS Package Restrictions

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