What is the Shipping Box Calculator?
Online sellers usually keep a few standard box sizes. The shipping box calculator checks your item (plus padding) against each one, in every orientation, and picks the smallest box that fits, keeping volumetric weight and courier charges low.
You can edit the list to match the boxes you stock. If none fits, use the Box Size Calculator to design a custom box; to compare courier charges use the Dimensional Weight Calculator. All calculators accept centimetres, inches or millimetres and kilograms or pounds, so you can use the units on your supplier's spec sheet.
How to use the Shipping Box Calculator
- Enter your item size and weight.
- Set the padding.
- Check or edit the list of standard boxes.
- Read the best-fit box and chargeable weight.
Example
A 28 × 18 × 8 cm item with 2 cm padding needs 32 × 22 × 12 cm. The smallest stock box that fits is 35 × 25 × 15 cm, chargeable at about 2.6 kg (÷5000).
Choosing stock box sizes
Analyse your best-selling products and choose 4–6 sizes that cover them with minimal empty space. Fewer sizes simplify ordering, while the right sizes reduce DIM charges and filler costs.
Related packaging and shipping tools
Packaging decisions are connected: the box size sets the volumetric weight, which sets the courier bill, and the carton size decides how many fit on a pallet or in a container. These related calculators help with the next step:
- Box size calculator: inside and outside box dimensions.
- Box volume calculator: volume in cm³, litres, CBM and ft³.
- Box weight calculator: empty carton weight from GSM.
- Corrugated box calculator: GSM and BCT strength.
- Cardboard sheet calculator: RSC blank size and sheet yield.
Frequently asked questions
How do I choose the right shipping box?
Pick the smallest box that fits the item plus padding.
Can I add my own box sizes?
Yes, edit the list.
Does it rotate the item?
Yes, it tries every orientation.
Why does box size affect shipping cost?
Couriers bill volumetric weight for large, light parcels.
What padding should I use?
2–3 cm for most goods; more for fragile items.
Is the Shipping Box Calculator free to use?
Yes. The Shipping Box Calculator on Custom Converter is completely free, with no sign-up, no daily limit and no watermark.
Does the Shipping Box Calculator work on mobile phones?
Yes. It is built mobile-first and works on Android phones, iPhones, tablets and computers in any modern browser, with no app to install.