How does pitch affect area?

We multiply the flat area by an approximate factor by slope (flat to steep).

Underlayment and flashing?

No — budget waterproofing and edge materials separately.

10% for simple roofs, more for complex ones.

For a first estimate only; rely on a contractor's site visit.

We use simplified bands (low/medium/steep) for an easy estimate.

Estimate roof area, material quantity, and cost, accounting for slope and waste.

Practical calculatorGeneral editable assumptionsGlobal-readyInteractive chart

Last updated: 2026-06-03

This calculator uses generic assumptions. Use advanced mode to override them for a more accurate result.

Source: default

roof = L × W × pitchFactor · adjusted = roof × (1 + waste)

How does pitch affect area?: We multiply the flat area by an approximate factor by slope (flat to steep).
Underlayment and flashing?: No — budget waterproofing and edge materials separately.
Suitable waste?: 10% for simple roofs, more for complex ones.
Enough to buy?: For a first estimate only; rely on a contractor's site visit.
Pitch in degrees?: We use simplified bands (low/medium/steep) for an easy estimate.

Results are estimates and not professional advice. Verify important decisions with a qualified professional.