Construction
Underlayment Calculator
Estimate roofing underlayment rolls from roof area, waste allowance, and roll coverage.
- Free to use
- Runs in your browser
- Level B · Industry formula
- Last reviewed 2026-08-16
Calculator guide
How to use the Underlayment Calculator
Estimate roofing underlayment rolls from roof area, waste allowance, and roll coverage. Enter the requested values and select Calculate. The result and supporting values are produced locally in your browser.
Formula
Worked example
A 1,800 ft² roof with 10% waste and 400 ft² coverage per roll requires 5 rolls.
What to keep in mind
- Use the manufacturer’s net coverage after required overlaps, not just nominal roll dimensions.
Methodology
This calculator uses deterministic arithmetic and performs the calculation locally in your browser. Verify assumptions, units, and source values for your specific use case.
Review standard: Level B · Industry formula. How calculator reviews work.
Frequently asked questions
What does this calculator calculate?
Estimate roofing underlayment rolls from roof area, waste allowance, and roll coverage.
How is the result calculated?
Rolls = ceil(Roof Area × (1 + Waste %) ÷ Coverage per Roll).
Can I use the result for an important decision?
Use the result as a calculation aid and verify the inputs, assumptions, and applicable professional or regulatory requirements before relying on it for an important decision.
Does CalculateMeasure store the values I enter?
The calculator performs its arithmetic in your browser. The calculator itself does not need to send your entered values to a server to produce the result.