Box Size Calculator — What Size Box Do I Need?

Enter your product's dimensions and how many units go in each box. We'll calculate the internal box size you should order, including padding, plus the dimensional (DIM) weight carriers will bill you for. When you're ready, order that exact size — every Build A Box box is made to your dimensions with no minimums that lock you out.

How it works: we test every arrangement of your units (rows × columns × layers) and pick the one that produces the smallest box, then add your padding allowance on every side and round up to the nearest 1/4 inch — that's the internal dimension you order. Dimensional weight uses the standard 139 divisor (UPS & FedEx daily rates) on outside dimensions; carriers bill whichever is greater, actual or DIM. Estimates only — final spec is confirmed with your order proof.