Roofing Calculator

Estimate roof area, roofing squares, shingle bundles, underlayment and drip edge from the house footprint and pitch.

/12
%
10% for simple gable roofs, 15% for hips and valleys.

Roof area

1,503 ft²

  • Roofing squares (with waste)16.5
  • Shingle bundles50
  • Underlayment rolls (≈400 ft² each)5
  • Drip edge (eaves + rakes)156 ft

Estimates only. Round up when you order, and confirm structural details with your local building code.

How to use it

  1. Enter the footprint and overhang.
  2. Enter the roof pitch.
  3. Pick the roofing material and waste.

The formula

Roof area = (length + 2 × overhang) × (width + 2 × overhang) × pitch multiplier

Squares = area ÷ 100; bundles = squares × 3

Worked example

House length (footprint)40 ft
House width (footprint)30 ft
Eave / rake overhang12 in
Roof pitch6 /12
Material3-tab / architectural shingles (3 bundles per square)
Waste10 %

Result

Roof area1,503 ft²
Roofing squares (with waste)16.5
Shingle bundles50
Underlayment rolls (≈400 ft² each)5
Drip edge (eaves + rakes)156 ft

Tips before you order

  • Add 10% waste for gable roofs and 15% for hips, valleys and dormers.
  • Order ridge cap and starter strip separately.

Questions

How many bundles of shingles in a square?

Three for most 3-tab and architectural shingles; some heavy designer shingles need four or five.