Box size calculator
Enter your product's size and weight and pick a box style. The calculator adds the clearance that style needs, rounds the inside size up to the next quarter inch, adds board thickness for the outside size, suggests a board, and works out dimensional weight with the 139 divisor UPS, FedEx and now USPS use. It runs on the same rules as the Tria Studio, so the size it gives you opens straight into a dieline.
Enter your product length, width and height in inches.
How the numbers are worked out
Inside size. Each style needs a different amount of room around the product: about 1/8 inch in total for a folding carton, 1/4 inch for a mailer, 5/16 inch for a shipping box and 1/2 inch for a rigid box, which usually carries an insert. Depth gets a little less, because the hand never reaches in from the top. The result is rounded up to the next quarter inch so the box is never tight.
Outside size. Board has thickness. 18 pt SBS adds about 0.02 inch per wall, E flute about 1/16 inch, B flute about 1/8 inch and rigid board about 1/12 inch. Lid-over-base styles add a second layer for the lid. Carriers charge on the outside, which is why it is shown.
Dimensional weight. Outside length, width and height are rounded up to whole inches, multiplied, and divided by 139. The carrier bills the larger of that and the real weight. Since July 12, 2026, USPS also uses 139 for packages over one cubic foot (1,728 cubic inches); under that, USPS bills on actual weight. Rates and rules change, so check your carrier account before you lock in a size.
Worked examples
| Product | Box | Inside (in) | Outside (in) | DIM weight | UPS, FedEx billable |
|---|---|---|---|---|---|
| A 3 oz serum bottle, 1.5 x 1.5 x 4.5 in tall | Auto lock bottom carton | 1.75 x 1.75 x 4.75 | 1.79 x 1.79 x 4.77 | 1 lb | 1 lb |
| An 8 oz candle jar, 3.25 x 3.25 x 3.75 in tall | Reverse tuck end carton | 3.5 x 3.5 x 4 | 3.54 x 3.54 x 4.02 | 1 lb | 1 lb |
| A folded hoodie, 11 x 9 x 3 in, 16 oz | Mailer box | 11.25 x 9.25 x 3.25 | 11.38 x 9.38 x 3.31 | 4 lb | 4 lb |
| A skincare set in a tray, 9 x 7 x 2.5 in, 20 oz | Magnetic closure rigid box | 9.5 x 7.5 x 3 | 9.66 x 7.66 x 3.08 | 3 lb | 3 lb |
| Two wine bottles side by side, 7 x 3.5 x 12.5 in, 6 lb | Shipping box (RSC) | 13 x 7.5 x 3.75 | 13.25 x 7.75 x 3.88 | 4 lb | 7 lb |
Carton sizes read length x width x height with the product standing; mailer, shipping and most rigid box sizes read with the product laid flat, which keeps dimensional weight down.
Want the drawing? Every size here opens in the Tria Studio, and there are free dieline templates for the common sizes of each style. When you are ready to order, the production dieline and a digital proof come free, from 200 units.