Box Size Calculator: Pick the Right Box
Find the inside and outside box dimensions for an item with the padding you need, and the dimensional weight FedEx and UPS will bill.
Typical padding: 2 in (5 cm) on every side for fragile items, 1 in for sturdy ones. Single wall corrugated is about 1/8 in (3 to 4 mm) thick, double wall about 1/4 in (6 to 7 mm).
Inside box size
16 × 13 × 8in
Outside box size
16.25 × 13.25 × 8.25in
Dimensional weight
16lb
FedEx and UPS (139)
Inside = item + 2 × padding; outside = inside + 2 × wall
Order boxes by inside dimensions (L × W × H, length the longest side of the opening). Carriers bill by outside size: dimensional weight uses the outside measurements, rounded up to whole inches.
How to choose a box size
The right box protects the item without paying to ship air. Too big and you pay dimensional weight and need more filler; too small and the item breaks. This calculator adds padding and the wall of the box to your item's size.
How to choose a box size
Inside size = item + 2 × padding on each dimension. Outside size = inside + 2 × wall thickness. A 12 × 9 × 4 in item with 2 in of padding needs a box 16 × 13 × 8 in inside.
Padding and board guide
| Item | Padding each side | Board |
|---|---|---|
| Books, clothing, sturdy goods | 1 in (2.5 cm) | Single wall |
| Electronics, ceramics, glass | 2 in (5 cm) | Double wall or box in box |
| Heavy items over 30 kg | 2 in plus internal bracing | Double or triple wall |
Why outside size matters
Carriers measure the outside of the box and round up to whole inches, then bill the higher of the actual weight and L × W × H ÷ 139 (FedEx and UPS). A box one inch bigger on each side can add several pounds of billed weight. See the dimensional weight calculator for other divisors.
Copy the result, or save it as a PDF to attach to an email or a purchase file. Nothing you type leaves your browser.
Features
- Item size plus padding
- Inside and outside size
- Wall thickness
- Inches or centimeters
- Dimensional weight (139)
- Copy or PDF
Frequently asked questions
Are box sizes inside or outside dimensions?
Box makers list inside dimensions, length × width × height. Carriers bill by outside dimensions.
How much padding do I need?
About 2 inches (5 cm) on every side for fragile items, 1 inch for sturdy ones.
What is single wall and double wall?
Corrugated board with one or two fluted layers. Double wall is about twice as thick and much stronger.
Is the calculator free?
Yes. No sign up. It runs in your browser, and you can copy the result or save it as a PDF.