What is the Corrugated Box Calculator?
Cartons at the bottom of a pallet carry everything above them, often for weeks in a humid warehouse. The corrugated box calculator estimates box compression strength (BCT) with the McKee formula from edge crush test (ECT), board caliper and box perimeter.
It then applies a safety factor for humidity and storage time to give a safe stacking load. For board GSM alone use the Corrugated Board Calculator; for box weight see the Box 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 Corrugated Box Calculator
- Enter box dimensions.
- Enter ECT (kN/m) and board caliper (mm).
- Choose a safety factor.
- Read BCT and safe stacking load.
Formula
BCT (N) = 5.87 × ECT × √(caliper × perimeter)
Example
A 40 × 30 cm box (perimeter 1,400 mm) with ECT 7 kN/m and 6 mm caliper gives BCT ≈ 5.87 × 7 × √8,400 ≈ 3,766 N (384 kgf). With a safety factor of 4, it can safely carry about 96 kg on top.
Safety factors
| Condition | Factor |
|---|---|
| Short storage, dry | 3 |
| Normal warehouse | 4 |
| Humid, long storage | 5+ |
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.
- Cardboard sheet calculator: RSC blank size and sheet yield.
- Box dieline generator: printable cut-and-fold template.
Frequently asked questions
What is BCT?
Box compression test: the load a box can take before collapsing.
What is the McKee formula?
A standard estimate of BCT from ECT, caliper and box perimeter.
What is ECT?
Edge crush test, the board's strength in kN/m.
Why use a safety factor?
Humidity, time and pallet overhang reduce real strength.
How do I increase box strength?
Use higher ECT board, double wall, or a more square box footprint.
Is the Corrugated Box Calculator free to use?
Yes. The Corrugated Box Calculator on Custom Converter is completely free, with no sign-up, no daily limit and no watermark.
Does the Corrugated 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.