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What your box bills at

Carriers charge a big, light box by its size, not its weight. Type in your box's outside measurements and its weight. You'll see the weight each carrier bills under the rules USPS brought in on July 12, 2026, the largest box that still bills on its actual weight, and what a smaller box would bill.

Measured on the outside. Decimals are fine: 15.2.

The box with everything in it.

Weight in
Add more detail (optional)3 of 3 filled

All three sides, at the same weight.

Your numbers stay in this page. Nothing is sent or stored.

Example shop, not yours yet. Type your numbers in the form and press “Work it out”.

What your box bills at

12 to 14 lb

14 lb with USPS, UPS Daily Rates and FedEx, 12 lb with UPS Retail Rates. The box's size sets the price, not its 3.2 lb.

The box

  • Sides as measured

    15.2 × 11.5 × 9.1 in

  • Sides rounded up

    each up to a whole inch

    16 × 12 × 10 in

  • Cubic inches

    16 × 12 × 10

    1,920

With USPS (Priority Mail, Ground Advantage)

  • Size weight

    1,920 ÷ 139 = 13.81, rounded up

    14 lb

  • Actual weight

    3.2 lb, rounded up to a whole pound

    4 lb

  • Billable weight

    the larger: the size weight

    14 lb

With UPS on Daily Rates

  • Size weight

    1,920 ÷ 139 = 13.81, rounded up

    14 lb

  • Actual weight

    3.2 lb, rounded up to a whole pound

    4 lb

  • Billable weight

    the larger: the size weight

    14 lb

With UPS on Retail Rates

  • Size weight

    1,920 ÷ 166 = 11.57, rounded up

    12 lb

  • Actual weight

    3.2 lb, rounded up to a whole pound

    4 lb

  • Billable weight

    the larger: the size weight

    12 lb

With FedEx

  • Size weight

    1,920 ÷ 139 = 13.81, rounded up

    14 lb

  • Actual weight

    3.2 lb, rounded up to a whole pound

    4 lb

  • Billable weight

    the larger: the size weight

    14 lb

Largest box that still bills the actual 4 lb

  • USPS

    1 cubic foot: no size weight up to there (4 lb × 139 is only 556)

    1,728 cubic inches

  • UPS Daily Rates

    4 lb × 139

    556 cubic inches

  • UPS Retail Rates

    4 lb × 166

    664 cubic inches

  • FedEx

    4 lb × 139

    556 cubic inches

With the smaller box, at the same weight

  • Sides rounded up

    10 × 8 × 6 in, each up to a whole inch

    10 × 8 × 6 in

  • Cubic inches

    10 × 8 × 6

    480

  • USPS

    1 cubic foot or less: no size weight; actual 4 lb; 10 lb less than the first box's 14 lb

    4 lb

  • UPS Daily Rates

    size weight 480 ÷ 139, rounded up, 4 lb; actual 4 lb; 10 lb less than the first box's 14 lb

    4 lb

  • UPS Retail Rates

    size weight 480 ÷ 166, rounded up, 3 lb; actual 4 lb; 8 lb less than the first box's 12 lb

    4 lb

  • FedEx

    size weight 480 ÷ 139, rounded up, 4 lb; actual 4 lb; 10 lb less than the first box's 14 lb

    4 lb

Cubic pricing at USPS (information)

  • Sides rounded down

    each down to the quarter inch, the other way from the size weight

    15 × 11.5 × 9 in

  • Cubic feet

    15 × 11.5 × 9 ÷ 1,728

    0.898

  • Ground Advantage cubic step

    1 cubic foot or less, 20 lb or less, longest side 22 inches or less: priced by size, in steps of 0.1 cubic foot

    0.9 cubic foot

The fix

  • A smaller box

    A box that bills the actual 4 lb, with each side rounded up: up to 1,728 cubic inches with USPS, up to 556 cubic inches with UPS Daily Rates and FedEx, up to 664 cubic inches with UPS Retail Rates. USPS also needs length plus girth of 108 in or less to price it by weight.

Good to know

  • As measured the box is 1,590.68 cubic inches, 1 cubic foot or less. With each side rounded up it's 1,920 cubic inches, over 1 cubic foot, so USPS charges it by size.
  • Only the weight each carrier bills is shown, not the label price: that depends on the zone (how far the box goes), your account and any surcharges. The label is priced at the billable weight.
  • These are the carriers' published rules. Your divisor can depend on your account: labels bought through a platform or a label site, such as Etsy or Pirate Ship, can come with their own terms (Pirate Ship's help page says its domestic UPS labels use 166). Check what your label account uses.
  • Carriers measure boxes again. If they find a bigger size or weight than the label says, they charge the difference later (Etsy, for one, takes USPS adjustments from your Payment account). Measure the outside of the box, bulges included.
  • USPS changed its rules on July 12, 2026: the divisor went from 166 to 139, and each side is now rounded up to a whole inch instead of to the nearest inch.
  • USPS Ground Advantage cubic (a commercial price, for labels bought online) prices a box by its size instead of its weight: 1 cubic foot or less, 20 lb or less and a longest side of 22 inches or less, in steps of 0.1 cubic foot, with each side rounded down to the quarter inch (the size weight rounds up). This box measures 15 × 11.5 × 9 in that way, 0.898 cubic foot: the 0.9 step. Priority Mail cubic takes up to 0.5 cubic foot. Whether cubic costs less than the weight price depends on the zone: compare the two when you buy the label.
  • For boxes only. Tubes and other odd shapes follow other rules (USPS multiplies their size by 0.785 first), and soft mailers are measured another way for cubic prices.
  • Very large or heavy boxes can carry extra handling or size charges with each carrier. They aren't counted here.
  • Amazon's fulfillment fees (FBA) size a unit their own way; this is for labels you buy and ship yourself.
  • Not affiliated with USPS, UPS or FedEx.
  • We assumed: Weight in the other box: 3.2 lb, the same. A smaller box often weighs a little less; the same weight is counted.

Carrier rules as of October 15, 2026: USPS from the Federal Register rule and the Domestic Mail Manual (in force since July 12, 2026), UPS from ups.com, FedEx from its 2026 Service Guide (updated September 11, 2026). Fixed formulas; no AI computes a number. Billable weight only: no label prices.

The rates this uses

Each one links to where it comes from, with that page’s date and the day we checked it. See every rate we use.

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Further reading