About this calculator

Estimate box compression strength with the simplified McKee relation using the measured edge crush test (ECT), board caliper and inside perimeter. It is an empirical estimate, not a laboratory box compression test (BCT) result.

Inputs

How to use this calculator

Box scenario

  1. Inside length (in)Use inside dimensions in the simplified McKee perimeter term.
  2. Inside width (in)Use inside dimensions in the simplified McKee perimeter term.
  3. Edge crush test (ECT), lb/inEnter a measured board ECT value in lb/in. This property remains lb/in in metric mode.
  4. Board caliper (in)Measured board thickness; the formula uses inches after unit conversion.

Enter the shipment or scenario values, then select Calculate result.

Method

Formula and variables

Simplified McKee estimate: box compression test (BCT) force (lb) = 5.87 × edge crush test (ECT) value (lb/in) × sqrt[inside perimeter (in) × board caliper (in)]. Perimeter = 2 × (inside length + inside width).

Inside length (in)
Use inside dimensions in the simplified McKee perimeter term.
Inside width (in)
Use inside dimensions in the simplified McKee perimeter term.
Edge crush test (ECT), lb/in
Enter a measured board ECT value in lb/in. This property remains lb/in in metric mode.
Board caliper (in)
Measured board thickness; the formula uses inches after unit conversion.

Interpret the result

The estimated box compression test (BCT) value is a compression-force prediction for the stated model. Do not substitute it for tested strength or a complete warehouse stack assessment.

Outputs: Estimated box compression strength (BCT)

Empirical estimate for a regular slotted corrugated box using measured board values. It is not a box-compression test result or guaranteed stacking capacity. Moisture, box style, score and slot geometry, manufacturing variation, printing, storage time and handling can change actual strength. Use a laboratory box-compression test for a measured result.

Worked example

Check the arithmetic

This example uses the starting values shown above. The arithmetic below is calculated independently of the interactive result.

Work through the calculation

  1. Inside perimeter = 2 × (12 + 10) = 44 in.
  2. BCT = 5.87 × 32 × sqrt(44 × 0.25) = 622.9948006 lb, displayed as 622.995 lb estimated BCT.

Compare the displayed result

Expected displayed result: 622.995 lb estimated BCT

FAQs

Does metric mode convert the ECT field?

The edge crush test (ECT) value remains in lb/in. Length and caliper measurements convert, but the measured ECT value must use the fixed unit shown in the field label.

Example inputs and options

Starting values are examples unless a field identifies a dated rule. Unit selectors convert only fields marked for conversion. Rates and model options keep the units and basis shown in their labels.

Inside length (in)
Example: 12
Inside width (in)
Example: 10
Edge crush test (ECT), lb/in
Example: 32
Board caliper (in)
Example: 0.25