Box compression strength calculator
Estimate how much top load a corrugated box can take, using the McKee formula.
How it works
The McKee formula is the industry's standard estimate of box compression strength (BCT), the top load a box can carry before it buckles:
Box height barely matters within normal proportions; what counts is the board's edge crush strength, its thickness, and the box's perimeter. That's why bigger boxes of the same board are stronger in compression.
A lab BCT is the strength of a new box in ideal conditions. Humidity, time under load, pallet overhang and handholes all reduce it, so warehouses divide by a safety factor, typically 3 to 5. Take the safe load to the box stacking calculator.
Results are estimates based on typical industry values. Confirm final specifications with your supplier or carrier.
Frequently asked questions
What is a good box compression strength?
It depends on the load. A 16 × 12 in 32 ECT C-flute box is typically around 550 to 600 lbf, enough for moderate stacking with a safety factor.
How accurate is the McKee formula?
Usually within about 10% for regular slotted containers. Real boxes vary, so test critical packaging.
Related articles
- Box compression strength and the McKee formula
What box compression strength (BCT) means, how the McKee formula estimates it from ECT and board caliper, and how to apply safety factors.
More box strength and weight tools
- Box stacking calculator
Find how many boxes can safely stack on top of one another.
- Packed box weight calculator
Add up everything in the box and see what you'll be billed for.