Roof Shingle Calculator
Roofing is counted in squares — 100 square feet, or 9.29 m². A bundle of three-tab shingles usually covers a third of a square, about 3.1 m², so three bundles make a square, but it varies by product, which is why coverage per bundle is an input. A 100 m² roof with 10% waste is 110 m²; 12 m of ridge, capped in a double layer, adds about 0.3 m² per metre for another 3.6 m², giving 113.6 m². Divided by 3.1 that is 36.6, so 37 bundles, or 12.2 squares.
Your numbers
Bundles needed
37bundles
Squares
12.23squares
Area
113.6m²
Formula
Bundles needed = ⌈(Roof area × (1 + Waste allowance ÷ 100) + Ridge and hip length × 0.3) ÷ Coverage per bundle⌉, Squares = Area ÷ 9.2903
Enter the true sloped roof area, not the footprint — convert it with the pitched roof calculator first or you will come up short. Roofs with many valleys and cut edges need more than a 10% allowance.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Roof area (m²)The roof’s horizontal plan area, seen from above. | 100 | 0 and up |
| Coverage per bundle (m²)The area one bundle covers — usually a third of a square, about 3.1 m², printed on the wrapper. | 3.1 | 0 and up |
| Ridge and hip length (m)The length along the top ridge and the hips — the runs that need a double layer of caps. | 12 | 0 and up |
| Waste allowance (%)The extra bought to cover breakage and offcuts. | 10 | 0 ~ 50 |
Step by step
Quick reference table
Results when only Roof area (m²) changes and everything else stays put.
| Roof area (m²) | Bundles needed (bundles) | Squares (squares) | Area (m²) |
|---|---|---|---|
| 50 | 19 | 6.31 | 58.6 |
| 75 | 28 | 9.27 | 86.1 |
| 100 | 37 | 12.23 | 113.6 |
| 150 | 55 | 18.15 | 168.6 |
| 200 | 73 | 24.07 | 223.6 |
What each result means
| Result | At default values |
|---|---|
| Bundles needed (bundles)Bundles to buy, rounded up, with waste and ridge caps already inside. | 37 |
| Squares (squares)The roofing trade unit; one square is 100 square feet, or 9.29 m². | 12.23 |
| Area (m²)The space a shape covers — length squared. | 113.6 |
Common mistakes
Enter the true sloped roof area, not the footprint — convert it with the pitched roof calculator first or you will come up short. Roofs with many valleys and cut edges need more than a 10% allowance.
Glossary
- Roof area
- The roof’s horizontal plan area, seen from above.
- Coverage per bundle
- The area one bundle covers — usually a third of a square, about 3.1 m², printed on the wrapper.
- Ridge and hip length
- The length along the top ridge and the hips — the runs that need a double layer of caps.
- Waste allowance
- The extra bought to cover breakage and offcuts.
- Bundles needed
- Bundles to buy, rounded up, with waste and ridge caps already inside.
- Squares
- The roofing trade unit; one square is 100 square feet, or 9.29 m².
- Area
- The space a shape covers — length squared.
Frequently asked questions
Q. How is Roof Shingle Calculator calculated?
Bundles needed = ⌈(Roof area × (1 + Waste allowance ÷ 100) + Ridge and hip length × 0.3) ÷ Coverage per bundle⌉, Squares = Area ÷ 9.2903 — Roofing is counted in squares — 100 square feet, or 9.29 m². A bundle of three-tab shingles usually covers a third of a square, about 3.1 m², so three bundles make a square, but it varies by product, which is why coverage per bundle is an input. A 100 m² roof with 10% waste is 110 m²; 12 m of ridge, capped in a double layer, adds about 0.3 m² per metre for another 3.6 m², giving 113.6 m². Divided by 3.1 that is 36.6, so 37 bundles, or 12.2 squares.
Q. Can you walk through an example?
With Roof area 100m², Coverage per bundle 3.1m², Ridge and hip length 12m, Waste allowance 10%, the answer is Bundles needed 37bundles.
Q. What do I need to enter?
Enter Roof area, Coverage per bundle, Ridge and hip length, Waste allowance. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Roof area (m²) moves the answer to Roof area (m²) 50 → Bundles needed (bundles) 19 and Roof area (m²) 200 → Bundles needed (bundles) 73. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Enter the true sloped roof area, not the footprint — convert it with the pitched roof calculator first or you will come up short. Roofs with many valleys and cut edges need more than a 10% allowance.
Related calculators
Keep your length units consistent across inputs — mixing centimetres and metres throws results far off.