How to use lumber waste allowance
What this calculation does
A waste allowance adds a user-selected percentage of extra stock to a net project quantity.
Enter the required usable quantity and a nonnegative overage percentage; do not enter a yield percentage here.
Enter the measurements
- Net requirement: Enter the net project quantity before overage.
- User-selected overage: Enter extra stock as a percent of the net amount.
Formula and variables
extra = net × overage / 100; gross = net + extra.
Gross quantity = net quantity×(1+overage percent÷100). The extra amount is gross minus net.
Read the result
Ten percent over 20 BF adds 2 BF and gives a 22 BF gross quantity.
Worked example
Inputs: 20 BF at 10% overage
- Extra = 20×10÷100 = 2 BF.
- Gross = 20+2 = 22 BF.
Expected result: 2 BF extra; 22 BF gross
Frequently asked questions
Is 10% a recommended allowance?
No. Enter an allowance selected for your own material and project.
Is overage the same as yield?
No. Waste percentage and usable yield use different formulas.
Conditions, presets and technical notes
User-supplied overage only. No universal waste rate is recommended; yield is a separate concept.