What this calculator does
Roof shingle bundles works out bundles of shingles needed, accounting for slope and waste. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaRoof area = plan area × slope factor; squares = area / 9.29 m²; bundles = squares × 3
The inputs explained
| Field | What to enter |
|---|---|
| Roof plan length (m) | A number, measured in m. Starts at 12. |
| Roof plan width (m) | A number, measured in m. Starts at 8. |
| Slope factor | A number. Starts at 1.15. |
| Waste allowance (%) | A number, measured in %. Starts at 10. |
| Bundle coverage (m²) | A number, measured in m². Starts at 3.1. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with roof plan length
Every other input is held at the calculator’s starting values while roof plan length varies. Select any row to load that scenario into the calculator.