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 package restrictions does USPS have?

The chart below shows the USPS First-Class Mail and First-Class Package service item size and weight restrictions.

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: 3 ½" x 5 ½"
  • Max: 4 ¼" x 6"
Must be a flat surface
Letter
  • Min: 3 ½" x 5 ½"
  • Max: 6 ⅛" x 11 ½"
Maximum weight is 3.5 oz.
Flat
  • Min: over 6 ⅛" x 11 ½"
  • Max: 12" x 15"
Maximum weight is 13 oz.
Parcel
Maximum size is 108" in combined length and girth (distance around the thickest part). First-Class™ Package Service packages cannot exceed 22" x 18" x 15".
Maximum weight for Priority Mail Express, Priority Mail, Library Mail, or Media Mail® is 70 lbs. First-Class™ Package Service packages must weigh less than 16 oz.
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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