Medium Priority Mail Box Cost: Current Prices & Fees

The medium Flat Rate box is the middle size of the three boxes USPS sells for Priority Mail. You pay one price for the box no matter what it weighs inside the limit, which makes it a popular choice for heavy or dense items that would cost more to ship by weight.

Prices on this page come from USPS Notice 123, the official price list effective October 4, 2026, and were checked on Oct 14, 2026. USPS adjusts prices about twice a year, so see the current Notice 123 for any change.

Retail prices apply when you buy postage at a post office or at the counter without a business account. The box itself is free at the post office and on USPS.com, and the price covers the shipment.

The medium size comes in two shapes, and both carry the same price. Pick the shape that fits your item. Since price is based on the box, fill it well, because a half-empty box costs the same as a full one.

Business customers who print postage through an online platform or a commercial account pay lower prices than the retail counter. This is the price table USPS lists for commercial customers.

The commercial price for the medium box is lower than retail. If you ship often, compare the savings against any monthly fee for the platform you use.

A Flat Rate box ships for the same price within the box's weight limit, and USPS publishes that limit in its service rules. If you can fit more by weight than the box holds by volume, flat rate shines. If the contents are light, a weight-based service may cost less, so compare both before you pick.

• Retail or commercial. Commercial prices are lower than the retail counter.
• Box size. Small, medium and large each have a fixed price.
• Contents. Items cannot be forced past the box closure, since a bulging box can be charged differently.
• Extras. Insurance beyond what is included, signature confirmation and similar services are extra.
• Destination. Domestic flat rate prices do not change by distance, which makes them useful for cross-country parcels.

Flat rate pricing helps most when the parcel is heavy for its size and the destination is far away. Books, tools, canned goods or small hardware often fit the case. For a light parcel going a short distance, Ground Advantage or even the small Flat Rate box may cost less. It helps to price your parcel both ways at the counter or online before you choose.

You can also compare against the Priority Mail Flat Rate envelope, which costs less but holds only flat items.

You can pay at a post office counter, or print a label on USPS.com and drop the box at a collection point or hand it to your carrier. Online labels are a convenience for retail customers, and the price shown in the retail table applies. Business shippers using commercial pricing buy through an approved platform instead.

Close the box without forcing it, and tape all the seams. Use padding to keep items from shifting. Do not alter the box, since USPS requires the box to be used as supplied for flat rate pricing. Write the address on the label, not on the box flaps.