Carton Size Calculator
Enter the carton length and width, the weight of each packed carton, how many you stack and the board grade. The calculator estimates the box compression strength with the McKee formula, the load on the bottom carton and whether it holds with a safe margin.
- Box compression strength
- Stack height
- Board grade
A safety factor of 4 allows for damp, time in storage and uneven pallets.
A carton's strength comes from its board and its perimeter. The McKee formula links box compression strength to the board's edge crush test value and the box perimeter. A 16 × 12 in carton in 32 ECT board holds about 560 lbf. With 20 lb cartons and a safety factor of 4, it can safely stack about 8 high.
Carton strength chart
16 × 12 in carton. Search for a board.
| Board | Strength (lbf) | Safe top load at ×4 (lb) |
|---|---|---|
| 32 ECT single | 562 | 141 |
| 44 ECT single | 773 | 193 |
| 48 ECT double | 1096 | 274 |
| 61 ECT double | 1418 | 354 |
| 71 ECT double | 1708 | 427 |
McKee estimate.
Stack height and load
16 × 12 in, 32 ECT, 20 lb cartons. Slide how many are stacked.
The bottom carton turns red when the stack is too heavy for it.
How to check carton strength
Board to stack. Step through it.
Measure
Length and width.
Columns stacked straight are far stronger than interlocked stacks, which can lose up to half their strength.
Single, double or triple wall
Board types. Compare them.
Common.
Sturdy.
Heavy duty.
Bigger cartons have a longer perimeter, so the same board stacks a little stronger.
Before you stack
Stack checks. Tick each item.
Tick each item as you go.
Never let cartons overhang the pallet edge. Overhang can cut strength by a third.
What you get
Carton strength. Each tile explains one result.
lbf and kgf.
On the bottom.
Factor.
Holds or not.
Cartons.
Humidity is the big weakness of cardboard. At high humidity strength can fall by half.
Frequently Asked Questions
No question matches that search.
How do I work out carton stacking strength?
Use the McKee formula, five point eight seven times the edge crush value times the square root of perimeter times board thickness.
What does ECT mean on a box?
Edge crush test, the force a strip of board takes on its edge, in pounds per inch.
What safety factor should I use?
Around four for normal warehouse storage, and five for damp or long storage.
How high can I stack cartons?
Until the load on the bottom carton reaches its strength divided by the safety factor.
Is double wall board twice as strong?
Roughly, as it has higher ECT and is thicker.
Does carton size change strength?
Yes. A bigger perimeter carries more load with the same board.
Why do stacked boxes collapse?
Damp, overhang, interlocked stacking or too much weight on the bottom box.
Stacks that stay standing
Check the board against the stack before you load the pallet, and your cartons arrive square.
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