Box compression strength calculator
Work out a rough estimate of how much load a carton can take using your own figures. Check the assumptions before you act on the result.
Your figures
Result
- Box strength
- 336.52 unit dependent [VERIFY]
How it is worked out
McKee: box strength = 5.87 x edge crush value x square root of (box perimeter x board thickness), units as stated on the page [VERIFY with your board supplier]
box_strength = 5.87*edge_crush_value*sqrt(box_perimeter*board_thickness)
Check before you rely on it. Verify consistent McKee units and suitability with a packaging engineer. Have an accountant or the right specialist check any figure that affects tax, a legal duty, safety or a large purchase.
What it works out
The box compression strength calculator turns records from the business into a figure for this decision: a rough estimate of how much load a carton can take. Use it when the responsible production or costing manager needs a consistent answer for this specific task. The answer uses only the values entered. Record the measurement period beside it.
What you need
| Input | Unit | Where to find it |
|---|---|---|
| Edge crush value (example: 6.20 ECT (verify unit)) | ECT (verify unit) | Enter edge crush value using the current job, register or approved business plan. |
| Box perimeter (example: 190 mm) | mm | Enter box perimeter using the current job, register or approved business plan. |
| Board thickness (example: 0.45 unit dependent [VERIFY]) | unit dependent [VERIFY] | Measure board thickness on the packed article, drawing, scale or approved specification. |
Use the same item, period and measurement unit for related inputs. If a figure comes from an estimate rather than an actual record, mark it as estimated. Keep your original figures beside the result.
The formula
In plain words, calculate box strength using the measured inputs below. The expressions are shown without hidden rounding so they can be checked by hand.
- box strength:
box_strength = 5.87*edge_crush_value*sqrt(box_perimeter*board_thickness).
Formula basis from the supplied taxonomy: McKee: box strength = 5.87 x edge crush value x square root of (box perimeter x board thickness), units as stated on the page [VERIFY with your board supplier]. Keep the given formula basis unchanged, but validate units before implementing the live calculator.
A worked example
Illustrative example: a service company uses the figures in the table above. These are example inputs, not industry averages. For this example, the main figures are edge crush value: 6.20 ECT (verify unit), box perimeter: 190 mm, board thickness: 0.45 unit dependent [VERIFY].
- Box strength:
5.87*edge_crush_value*sqrt(box_perimeter*board_thickness). With the example figures,5.87 * 6.2 * sqrt(190.0 * 0.45)gives 336.52 unit dependent [VERIFY].
How to act: Use the result to test the estimate against one physical sample. Write down the input date and the assumption that could move most.
How to read the result
Example bands, change them for your business:
- Comfortable: Your result meets the target for this item or reporting period. Keep the calculation with its source records and test the estimate against one physical sample.
- Watch: The result is close to your action limit, or it changed since the previous calculation. Recheck edge crush value and box perimeter using the original records.
- Act: The result breaks a limit already agreed by the manager or owner. Record the difference, name a responsible person, and agree a correction date. For an operational starting point, read [Quoting without real cost](/problems/quoting-without-real-cost) and [Costing a new part](/processes/costing-a-new-part). Do not use these example bands as published industry benchmarks.
Copy it into a spreadsheet
Create a sheet with column A for the label and column B for the number or formula. The expressions work in Excel or Google Sheets. Keep input cells editable and result cells protected from typing.
| Cell | Label | Value or formula |
|---|---|---|
| B2 | edge crush value | 6.200000 |
| B3 | box perimeter | 190.000000 |
| B4 | board thickness | 0.450000 |
| B6 | box strength | =((5.87*B2)*SQRT((B3*B4))) |
For any formula containing a divisor, enter a value above zero. For any monetary output, format the cell in Indian rupees. Do not replace the cells with rounded figures until the final display.
What this calculator leaves out
- Process loss, material grade, production method and customer tolerance may change the result.
- The McKee expression is unit-sensitive and approximate. Confirm the ECT, perimeter and thickness unit system with a packaging engineer before using a strength result.
- The formula does not check whether the records are complete. Take dimensions and weights from the approved drawing, sample or batch record. Confirm the unit before typing.
Common mistakes
- Mixing periods. Using edge crush value from one month with box perimeter from another produces a number that looks precise but is hard to act on.
- Trusting old figures. Recheck the relevant source record before reusing last month's saved inputs. Check a trial sample against the calculated amount before committing a large order.
- Treating an estimate as approval. Record which assumptions were entered by hand. Get the relevant owner, accountant or technician to check unusual values.
A number like this helps only if someone works it out again when things change.
Questions people ask
Where do I find the numbers for box compression strength calculator?
Enter edge crush value using the current job, register or approved business plan. Enter box perimeter using the current job, register or approved business plan. Keep all inputs from the same period.
Can I use this number to approve a purchase or payment?
Use it as a first check. Use the result to test the estimate against one physical sample. Write down the input date and the assumption that could move most. If the result affects tax, legal duties, workplace safety or a major investment, obtain the appropriate review.
When should I calculate it again?
Recalculate when a meaningful input changes, and at the next regular review of the relevant register. Save the date and the input values so changes can be explained.
FORMULA NOTE: The supplied McKee coefficient depends on ECT, perimeter and thickness units. The source does not specify a consistent unit system; engineering verification is mandatory.