What is flat rate shipping?
Flat rate shipping is one fixed shipping price, whatever the parcel weighs or wherever it goes. Your store can charge every order the same fee, say $8. Or a carrier can charge one price per box: on November 10, 2026, a USPS Small Flat Rate Box cost $14.65 at the Post Office.
How does flat rate shipping work for a store?
Each order pays your $8 fee once, so four hats pay $8, not $32. Say labels run from $5 next door to $14 across the country, averaging $8. Near orders pay for far ones. One heavy order to a remote address can still cost several times your fee. Shopify calls this rate type "Flat", and Shopify shipping rates has the steps.
Flat rate vs free shipping vs calculated rates
A flat rate fits when your labels land in a narrow range. Calculated rates price each parcel at checkout by weight, size and distance. Free shipping moves the cost into your prices. It often starts at a free shipping threshold, with a flat rate below it.
What is USPS flat rate shipping?
USPS Priority Mail Flat Rate charges one price per box or envelope to any US address, up to 70 lb. USPS's Priority Mail page listed these on November 10, 2026:
| Package | At a Post Office | Commercial, bought online |
|---|---|---|
| Flat Rate Envelope | $13.90 | $11.97 |
| Small Flat Rate Box | $14.65 | $12.95 |
| Medium Flat Rate Box | $25.80 | $22.02 |
| Large Flat Rate Box | $36.10 | $32.75 |
Those prices carry a holiday increase that ends January 17, 2027. A Flat Rate box pays off on a heavy, compact parcel going far. Sent more than about 1,800 miles, a 10 lb parcel costs $63.40 by weight at a Post Office, against $25.80 in a Medium box. To the nearest zone, a 1 lb parcel costs $11.50 by weight, less than the Small box.
Where do you get flat rate shipping boxes?
USPS's online store sends Flat Rate boxes free, with your mail, usually within 7 to 10 days. The Small box is 8 5/8 x 5 3/8 x 1 5/8 inches inside, and the Large is 12 x 11 3/4 x 5 1/2. Only USPS's own box gets the price, not a plain box the same size, as Shopify's Help Center notes. UPS Simple Rate prices by box size and speed and takes your own box, up to 1 cubic foot and 50 lb. FedEx One Rate needs FedEx's free packaging.
Show shoppers how close free shipping is, with Sledge
Sledge sets no shipping rates. On every plan, the Progress goal bar in its Cart Drawer can hold a Free shipping reward. At your goal, the shipping discount you set comes off at checkout. On a paid plan, Growth Intelligence totals its suggested fixes into one figure in your store's currency, labeled "Est. potential".
