Use these rulers and guide boxes to measure letters and large envelopes.
Once a piece of mail exceeds the maximum length, height, or thickness of one shape, it automatically gets classified as the next largest shape.
Minimum size for Postcards and Letters
5" long x 3-1/2" high
Maximum size for Postcards
6" long x 4-1/4" high
Maximum size for Letters
11-1/2" long x 6-1/8" high
Maximum thickness for Letters
Maximum thickness for Large Envelopes
Large Envelopes exceed one of the letter size maximum dimensions.
Unusual Shapes and Sizes
Sometimes a piece of mail
requires additional postage
because it is a certain shape or
size that is difficult to process on
mail sorting machines. To make
sure you’re paying the correct
postage, visit pe.usps.com. These
are examples of mail that could
require additional postage:
· Square envelopes
· Envelopes on which the address is written parallel to the shorter edge square