USPS Flat Rate Box Sizes & Prices

Envelope

Flat Rate Envelope

12-1/2" x 9-1/2" inside

$11.97online · $13.90 at the Post Office

Good for documents and photos, a folded T-shirt, a paperback book.

Envelope

Legal Flat Rate Envelope

15" x 9-1/2" inside

$12.51online · $14.25 at the Post Office

Good for legal-size contracts, a pair of leggings, long flat prints.

Envelope

Padded Flat Rate Envelope

12-1/2" x 9-1/2" inside

$12.84online · $15.00 at the Post Office

Good for a hoodie or sweater, a boxed phone, a video game in its case.

Box

Small Flat Rate Box

8-5/8" x 5-3/8" x 1-5/8" inside

$12.95online · $14.65 at the Post Office

Good for a phone, jewelry, a video game.

Box

Medium Box (Top-Loading)

11" x 8-1/2" x 5-1/2" inside

$22.02online · $25.80 at the Post Office

Good for a pair of sneakers, 3 to 5 hardcover books, a small kitchen appliance.

Box

Medium Box (Side-Loading)

13-5/8" x 11-7/8" x 3-3/8" inside

$22.02online · $25.80 at the Post Office

Good for a 13-inch laptop, folded jeans and hoodies, board games.

Box

Large Flat Rate Box

12" x 11-3/4" x 5-1/2" inside

$32.75online · $36.10 at the Post Office

Good for a stack of 8 to 10 books, a 15-inch laptop in its box, several pairs of shoes.