Roof Area Calculator
Roof Area Calculator
Working on a roofing project? This roof area calculator helps you quickly estimate the total surface area of your roof based on pitch, span, and length. Perfect for working out tile requirements, underlay coverage, and material costs — suitable for builders, roofers, and DIYers in the UK and USA.
Technical Guidance
- UK: Roof area = length × width × pitch factor (use table below)
- USA: Same method, but use feet and inches — roof squares = total ft² ÷ 100
- Dual-pitch roofs = calculate one slope and double it (if equal)
- Use actual roof slope length, not just wall footprint
Roof Pitch Factors
| Pitch Angle | Pitch Ratio | Multiplier (Area Factor) |
|---|---|---|
| 15° | 3:12 | 1.04 |
| 30° | 7:12 | 1.15 |
| 45° | 12:12 | 1.41 |
| 60° | 17:12 | 1.73 |
Pro Tips
- Measure both roof sides if it's not a symmetrical gable
- Include overhangs in your total roof width and length
- For complex roofs (hip, L-shape), break it into rectangles and add them up
Common Mistakes
- Forgetting pitch factor — leads to underestimating material
- Mixing horizontal dimensions with slope calculations
- Not accounting for dormers, skylights, or valleys
FAQs
- How do I measure a pitched roof? → Use tape measure on the slope (not flat) or calculate from pitch angle
- What’s a roof square? → 1 roofing square = 100 ft² of area (used mostly in USA)
- Can I use this calculator for metal and tile roofs? → Yes, it works for any material — just match the area to the product coverage
