Roofing Calculator

Feet or metric — e.g. 40' or 12 m

Feet or metric — e.g. 30' or 9 m

Rise per 12″ of run. 0 = flat.

1342 sq ft · 124.6 m²

Roof area

14.8 sq

Squares (+10% waste)

40' × 30' @ 6:12

Shingle bundles (~3/square)45 bundles
Slope factor1.118 (6:12)
Footprint1200 sq ft

Assumptions & notes

  • Slope factor 1.118 at 6:12 — roof area is the 1200 sq ft footprint × that factor.
  • A "square" is 100 sq ft. Order ~10% extra for waste, starter, and hip/ridge caps (typical — check your product).
  • Bundles assume ~3 per square (typical 3-tab / architectural). Complex roofs — dormers, valleys, overhangs beyond the footprint — add area; measure or add margin.