Roofing felt calculator
Supply all values for the chosen model. Enter zero explicitly when appropriate. This estimates area quantities; it does not optimize cutting, specify manufacturer laps, or certify roof installation or structure.
A QUICK WALKTHROUGH
How to use this tool
- Planes: length, width (m), one pair per line, 1–100
- Extra penetration/upstand area (m²)
- Waste (%)
- Coverage model: Percentage area loss / Side and end laps
- Comparison field
Coverage model
Interior effective area = (roll width − side lap) × (roll length − end lap). Required = (sum of plane areas + extra) × (1 + waste / 100). Rolls = ceil(required / effective).
Plane areas / Comparison field
Planes: length, width (m), one pair per line, 1–100; Extra penetration/upstand area (m²); Waste (%). Supply all values for the chosen model. Enter zero explicitly when appropriate. This estimates area quantities; it does not optimize cutting, specify manufacturer laps, or certify roof installation or structure.
GOOD TO KNOW
Common questions
Coverage model
Percentage area loss / Side and end laps. Supply all values for the chosen model. Enter zero explicitly when appropriate. This estimates area quantities; it does not optimize cutting, specify manufacturer laps, or certify roof installation or structure.
Extra penetration/upstand area (m²)
Extra penetration/upstand area (m²); Interior effective area = (roll width − side lap) × (roll length − end lap). Required = (sum of plane areas + extra) × (1 + waste / 100). Rolls = ceil(required / effective).