Roof Covering, Underlay and Gutter Calculator
Plan roof covering bundles, underlay rolls and gutter sections from footprint, pitch and waste allowance.
Formula
Planning estimate. Check product specifications and local requirements before purchasing.
Worked example: Roof Replacement Project Calculator
Measurements in this example
| Length | 10 m |
|---|---|
| Width | 8 m |
| Roof angle | 30 ° |
| Coverage per bundle | 3 m² |
| Underlay coverage per roll | 40 m² |
| Piece length | 3 m |
| Waste allowance | 10 % |
Calculated quantities
| Area with allowance | 101.61 m² |
|---|---|
| Whole bundles | 34 |
| Underlay rolls | 3 |
| Whole gutter sections | 8 |
What to check
This calculation uses: Length, Width, Roof angle, Coverage per bundle, Underlay coverage per roll, Piece length, Waste allowance. It returns: Area with allowance, Whole bundles, Underlay rolls, Whole gutter sections.
Split the roof into simple slopes and measure each one. Valleys, hips, dormers and penetrations need separate allowance.
Flashing, underlay, ridge pieces, valleys, fasteners and drainage capacity are separate parts of the roof system.
Use the units beside each field. The values in the worked example are starting inputs; replace them with your measurements and the specifications of your material.
Compare alternatives
Open a tool, enter your measured dimensions, then save an estimate. Keep another version if you want to compare products or allowances.