Roof materials
Sheathing waste calculator
Estimate sheathing area allowance. Hip or valley roof with a selected waste percentage.
Try the calculation
Show the gross area after the selected allowance.
Adjustable example. Change these illustrative inputs to match your task, then recalculate. Reset restores the example and its result.
Understand the result
How this calculation works
Sheathing waste adds a percentage to net measured area.
Steps
- Enter net roof area and the allowance you want to compare.
- The result is gross area, not a sheet count.
The form starts with the worked example below. Change its values and selections to match your task; Reset restores the example.
Formula
gross area = net area × (1 + waste ÷ 100).
Variables and units
- Net area (sq ft)
- Required. Use a positive value. Starting example: 1200. Replace it for your task.
- Waste allowance (%)
- Required. Zero is accepted. Starting example: 10. Replace it for your task.
What the result means
Use the gross area as an input to a separate sheet or panel quantity estimate.
Worked example
Inputs: Net area = 1200; Waste allowance = 10.
Calculation: 1,200 sq ft × 1.10 = 1,320 sq ft.
Result: 1,320 sq ft gross.
Frequently asked questions
Can I use zero waste?
Yes, zero is an allowed assumption.
Does it know whether a roof is hip or valley?
No, the allowance is user supplied.
Does gross area equal purchased sheets?
No, sheet coverage and cut layout still matter.