What Is the Minimum Size of an Envelope That Can Go Through the USPS?


Quick Answer

According to the USPS, the minimum size of an envelope that can be mailed is 5 inches long by 3 1/2 inches high by 0.007 inches thick. The regulations also state that envelopes must be rectangular and not larger than 11 1/2 inches by 6 1/8 inches by 1/4 inches.

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Full Answer

The maximum weight should not exceed 3.5 ounces. Letters that do not meet these requirements can be still mailed, but the USPS may assess what it describes as a nonmachinable surcharge, as these parcels must be hand-sorted. The USPS may also apply the surcharge to letters that have clasp closures, are lumpy or do not bend easily.

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