Use our Priority Mail Flat Rate Envelopes or Boxes that come in standard sizes so you don't have to worry about measuring them.

April 5, 2026 - Outside: 11 ¼” x 8 ¾” x 6″ Inside: 11″ x 8 ½” x 5 ½” · Outside: 14″ x 12″ x 3 ½” Inside: 13″ x 5⁄8” x 11 7⁄8” x 3 3⁄8“ · As you can see while these 2 boxes are both considered to be “medium sized” they are vastly different in their dimensions and are ...

1 week ago - A 10-pound box that fits into roughly a 6" × 6" × 6" cube would cost approximately $10.98–$13.00 via Cubic depending on zone, compared to $21.20 in a Medium Flat Rate Box via Shippo.

January 5, 2026 - USPS flat rate boxes are free to order, but they can only be used with Priority Mail Flat Rate. They work best for heavy, compact shipments because the price stays the same up to 70 lbs, regardless of destination. In this guide, you’ll find the current USPS flat rate box sizes, prices, and when flat rate is cheaper than using your own box.

Weight restrictions for Priority Mail Express International Flat Rate Envelopes are 4 pounds. Weight restrictions for Priority Mail International Large and Medium Flat Rate Boxes are 20 pounds, and 4 pounds for Priority Mail International Flat Rate Envelopes and Small Flat Rate Priced Boxes. You ...

The Priority Mail Flat Rate® Large Box features predetermined rates regardless of weight (domestically) or destination, similar to other Flat Rate products. This item ships in single, or a pack of 10 or 25 boxes.

2 weeks ago - Here are some examples that illustrate how Flat Rate Packaging can be more expensive: Medium Flat Rate Box 1 dimensions: 11 x 8.5 x 5.5 inches · Medium Flat Rate Box 2 dimensions: 14 x 12 x 3.5 inches · If you used your own box that was the ...

16 hours ago - Every USPS Flat Rate box size, dimensions, retail and commercial pricing. Weight limits and when flat rate saves vs regular Priority Mail.

1 month ago - To ship with USPS Flat Rate, you need to use USPS Flat Rate boxes. Flat Rate boxes come in three main sizes: small, medium, and large.

March 1, 2026 - USPS offers free Priority Mail Flat Rate boxes in Small (8-11/16" x 5-7/16" x 1-3/4"), Medium (11-1/4" x 8-3/4" x 6" or 14-1/8" x 12" x 3-1/2"), and Large (12-1/4" x 12" x 6"), all up to 70 lbs.

October 29, 2025 - With USPS Flat Rate shipping, the same price applies no matter how far the package travels, as long as it fits within the box and doesn’t exceed the maximum weight. You get predictable flat rate pricing, which is perfect for store owners who want to simplify logistics. The postal service offers three main types of flat rate packaging: Flat Rate Boxes and Envelopes – Fixed-price boxes and envelopes in various sizes.

March 6, 2026 - The Small Flat Rate Box is among the smallest models in the flat rate. It is small, and this is why it fits items that have low volume and are also quite heavy. Although the size of the box is small, it can be safely used to transport objects that do not exceed 70 pounds, which is a tremendous benefit to the weight-based shipping strategies. Since the rate is charged statically, this box frequently happens to be the least expensive USPS delivery service for thicker objects that would otherwise be a lot more costly under regular Priority Mail rates.

April 8, 2025 - Size limits vary by box type: Small Flat Rate Box (8⅝" × 5⅜" × 1¾"), Medium Flat Rate Box (11¼" × 8¾" × 6" or 13⅝" × 11⅞" × 3⅜"), and Large Flat Rate Box (12¼" × 12¼" × 6").

Flat Rate option: Ship using free Flat Rate Boxes and Envelopes (envelopes and small boxes up to 4 lbs, medium and large boxes up to 20 lbs), starting at $32.65.

January 6, 2026 - Learn the Large Flat Rate USPS Box dimensions, 70 lb limits, 2026 prices, and when it’s cheapest vs Priority, Cubic, or Ground. Compare and save.

The Priority Mail Flat Rate® Medium Box is an easy way to ship featuring predetermined rates regardless of weight (domestically) or destination. This item ships in single, or a pack of 10 or 25 boxes.

March 20, 2026 - The most commonly used Flat Rate formats are the Flat Rate Envelope, Legal Flat Rate Envelope, Padded Flat Rate Envelope, Small Flat Rate Box, two Medium Flat Rate Boxes, and the Large Flat Rate Box. USPS also offers additional non-Flat-Rate Priority Mail and Priority Mail Express packaging in other shapes and sizes.

April 13, 2026 - Standard Priority Mail with right-sized packaging often costs less. Regional shipping makes zone-based rates competitive. Brands primarily serving customers within 600 miles (Zones 1-4) rarely benefit from Flat Rate’s zone-independence since local weight-based rates are already reasonable. Top loading flat rate boxes from USPS Priority Mail Flat Rate are designed for easy packing and extra protection, making them ideal for shipping fragile or awkwardly shaped items.

February 2, 2026 - If the flaps meet cleanly where they’re supposed to and the box looks like it did when USPS sent it to you (just filled), you’re good. If you’re pulling flaps together or the cardboard is stressed and bowing, size up. Real example from my Poshmark store: I shipped two pairs of jeans in a Medium Flat Rate Box.

The Priority Mail Flat Rate® Small Box is about the same size and shape as three stacked DVD cases. It is perfect for jewelry, electronics, event tickets, or other small items that need expedited shipping.