How this worksheet works
From roof area to whole rolls
Use installed coverage after laps—not nominal sheet area. The result separates required coverage from the whole-roll order and its remaining coverage.
How to use it
- Enter total sloped roof area.
- Enter a planning waste allowance and installed coverage per roll.
- Round up to whole rolls; verify lap requirements for the roof slope and assembly.
Useful for
- Synthetic underlayment estimates
- Felt roll estimates
- Comparing roll sizes and installed coverage
Assumptions
- Coverage per roll already reflects required laps
- All roof areas use the same underlayment
- Whole rolls are ordered
Limitations
- Ice barriers, valley membranes, and doubled coverage are separate
- Exposure, slope, and fastening rules can change installed coverage
- Does not plan seam locations
Common checks
Questions about this calculator
Should I enter nominal roll area?
Enter usable installed coverage after the required side and end laps whenever that figure is available.
Is ice-and-water membrane included?
No. Measure eaves, valleys, penetrations, and other required membrane areas separately.