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Box Size Calculator

Type the item's size, the padding you want on each side and its weight. The calculator finds the smallest common stock boxes that fit in any orientation and shows the dimensional weight each box would be billed at, so the cheapest box is obvious.

Item
in
in
in
in

1 in for fragile, 0.5 in for sturdy

lb

Smallest stock boxes that fit

  1. 12 × 9 × 6 in648 in³

    Item placed 11.0 × 8.0 × 5.0; slack 1.0 / 1.0 / 1.0 in. UPS/FedEx dim weight 5 lb vs actual 2 lb → billed at 5 lb.

  2. 14 × 10 × 6 in840 in³

    Item placed 11.0 × 8.0 × 5.0; slack 3.0 / 2.0 / 1.0 in. UPS/FedEx dim weight 7 lb vs actual 2 lb → billed at 7 lb.

  3. 12 × 10 × 8 in960 in³

    Item placed 11.0 × 8.0 × 5.0; slack 1.0 / 2.0 / 3.0 in. UPS/FedEx dim weight 7 lb vs actual 2 lb → billed at 7 lb.

  4. 12 × 12 × 8 in1152 in³

    Item placed 11.0 × 8.0 × 5.0; slack 1.0 / 4.0 / 3.0 in. UPS/FedEx dim weight 9 lb vs actual 2 lb → billed at 9 lb.

  5. 16 × 12 × 8 in1536 in³

    Item placed 11.0 × 8.0 × 5.0; slack 5.0 / 4.0 / 3.0 in. UPS/FedEx dim weight 12 lb vs actual 2 lb → billed at 12 lb.

Why the smallest box that fits is usually the cheapest label

Carriers bill the greater of actual weight and dimensional weight. A roomy box can double the billable weight of a light item: a 2 lb item in a 12 × 12 × 8 box is billed at 9 lb by UPS and FedEx, while the same item in a 10 × 8 × 6 box is billed at 4 lb. Over a few hundred shipments the box choice is worth more than most carrier discounts.

How the calculator chooses

  1. Adds your padding to every side of the item.
  2. Tries all six ways of orienting the padded item in each stock box.
  3. Keeps every box that fits and sorts them by volume, smallest first.
  4. Shows the slack on each axis so you know how much void fill to buy, and the dimensional weight at the 139 divisor.

Worked example

A 9 × 6 × 3 inch hardback book with one inch of padding needs an 11 × 8 × 5 inch space. The 11 × 8 × 4 box is an inch too shallow, so the smallest stock box that fits is 12 × 9 × 6, with an inch of slack on every side and a dimensional weight of 5 lb. Drop the padding to half an inch and 10 × 8 × 6 fits at 4 lb.

Questions sellers ask

How much padding should I allow?
About half an inch per side for sturdy items in their own packaging, one inch per side for anything fragile, and two inches for glass, ceramics and electronics with no retail box. Padding is added to every side, so one inch of padding adds two inches to each dimension.
Why does the calculator show dimensional weight?
Because the box you choose sets the dimensional weight the carrier bills. Two boxes that both fit can differ by several billable pounds. The list shows the UPS/FedEx dimensional weight of each box next to your actual weight so you can see which one is actually cheaper to ship.
The item fits diagonally. Does the calculator allow that?
No. It only places the item square to the box in one of the six orientations, which is how it will actually sit once padded. Diagonal placement leaves the corners unprotected.
Which box sizes are included?
Eighteen common stock sizes sold by US packaging suppliers, from 6 × 4 × 4 up to 24 × 18 × 18 inches. If none fits, a custom box or a two-piece telescoping box is the next step.

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