Methodology & sources
Each calculator on Roofing Cost Calculators uses a published, industry-standard formula. Below is the exact method behind every tool. Constants such as material densities follow common supplier and engineering references; local prices are user-entered so the estimate reflects your market.
| Tool | Formula |
|---|---|
| Roof Pitch Calculator | Angle = atan(rise ÷ 12). Slope factor = √(rise² + 12²) ÷ 12. Rafter = (span ÷ 2 + overhang) × slope factor. |
| Roofing Shingle Calculator | Squares = (Length × Width × pitch ÷ 100) × (1 + waste%). Bundles = ceil(squares × 3). Cost = bundles × price per bundle. |
| Roof Replacement Cost Calculator | Roof area = Length × Width × pitch factor. Squares = (roof area ÷ 100) × (1 + waste%). Installed cost = squares × (material price + labour price). |
Estimates exclude labour, delivery, tax and site-specific conditions unless stated. Always confirm with your supplier.