Box size calculator
Work out the inside size of your box from your product’s size and the room you want around it.
A rule of thumb. Your account manager confirms the size on the proof, and the 3D mockup shows the fit before you pay.
Quote this size →Questions
Inside or outside size?
Boxes are quoted by inside size, the space your product gets. The outside is slightly larger because of the board thickness.
How much room should I leave?
About 1/8 inch on each side is a common starting point for a snug retail box; leave more for padding or an insert. Your account manager confirms it on the proof.
Still have a question? Ask a packaging specialist.
Request a Quote →More free tools: Dimensional weight calculator · Box dieline generator (SVG, no login) · Label size & unwind calculator · Paperboard GSM to pt converter · Corrugated flute & ECT selector · Master carton & pallet calculator · Stand-up pouch size calculator · AI packaging DPI checker · Holiday packaging cutoff calculator
Embed the free box size calculator on your site
Ecommerce guides, 3PL fulfillment calculators, and design classrooms can embed this calculator for free. Copy the snippet below to add it to any page:
<iframe src="https://cubitpack.com/tools/box-size-calculator" width="100%" height="620" style="border:1px solid #e2e4ea;border-radius:12px;background:#fff;" loading="lazy" title="CubitPack Free Box size calculator"></iframe>
<p style="font-size:12px;color:#555;margin-top:6px;">Free tool by <a href="https://cubitpack.com/tools/box-size-calculator">CubitPack Box size calculator</a> · <a href="https://cubitpack.com/boxes">Custom Boxes</a></p>Popular custom packaging sized with this tool
Request a custom quote
One dedicated account manager prepares pricing across up to 3 quantities.
- Free design & AI-to-print studio + 3D mockup
- No die or plate charges · 4–5 day rush available
- Free shipping to all 50 states
- 10% off your first order
- Reprint or refund if we get it wrong