Minimum Size

If a mailpiece is 1/4 inch thick or less, it MUST be rectangular and at least 3-1/2 inches high by 5 inches long.

All mailpieces MUST be at least 0.007 inches thick.

Maximum Size

The maximum size for most mailpieces is 108 inches in combined length and girth. Standard Post[1] pieces may measure up to 130 inches in combined length and girth (but will be charged oversized prices).

Regardless of the size of the mailpiece, the maximum mailable weight of any mailpiece is 70 pounds. Some classes of mail have lower weight limits.

TIPS
- What is high? What is long? Length is the longest dimension, when first determining whether your piece is a letter, flat, or a parcel. Height is the side that is perpendicular to the length.
- 0.007 inches? How do I measure that? As a guide, an index card is thick enough. If in doubt, contact a mailpiece design analyst (MDA[2]) near you. MDAs have tools for precisely measuring thickness and can tell you if your mailpiece is thick enough.

Mailpiece shape[3]