How much does pitch add to roof area?

About 3% at 3/12, 12% at 6/12 and 41% at 12/12.

If every plane has the same pitch, the same factor applies to the whole footprint.

Can I measure a roof from satellite images?

Yes for the footprint; then apply the pitch factor.

How do I measure a hip roof?

If every plane has the same pitch, footprint × factor.

10% for gables; 15% with hips, valleys and dormers.

Roof area calculator

Plan length and width (with overhangs) and pitch: you get true roof area, pitch factor and roofing squares.

True roof area

92.38 m²

True roof area92.38 m²
Roofing squares (100 sq ft)9.94 squares
Floor plan area80 m²
Pitch factor1.15

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How it's calculated (visible formula)

area = plan × factor; factor = 1 ÷ cos(pitch); squares = sq ft ÷ 100

Net geometric measurement, no waste.
Adjustable waste % for cuts and breakage.
Purchase rounded up to sellable units (boxes, bags, buckets, boards).

See methodology and formula versions

How to calculate it, step by step

Measure the building footprint including overhangs.
Measure or estimate the pitch.
Pitch factor = 1 ÷ cos(pitch).
Multiply footprint by the factor.
Use true area to order material.

Worked example: 33 × 26 ft footprint, 7/12 pitch (30°)

Plan: 861 sq ft (80 m²)
Factor: 1 ÷ cos 30° = 1.155

→ 994 sq ft — 9.9 squares.

Common mistakes

Ordering from footprint area.
Leaving out overhangs.
One factor for planes with different pitches.

Pro tips

On complex roofs, measure each plane separately.
Add hips, valleys and ridges as linear feet.
Use satellite imagery or a drone if you can't climb.
Add waste for complexity (10–15%).

From calculation to quote

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FAQs

How much does pitch add to roof area?: About 3% at 3/12, 12% at 6/12 and 41% at 12/12.
What is a roofing square?: 100 sq ft of roof surface.
Hip roofs?: If every plane has the same pitch, the same factor applies to the whole footprint.
Can I measure a roof from satellite images?: Yes for the footprint; then apply the pitch factor.
How do I measure a hip roof?: If every plane has the same pitch, footprint × factor.
How much waste?: 10% for gables; 15% with hips, valleys and dormers.

Sources and standards

Maintained by Srikanta M · Formula v1.0.0 · Verified 2026-09-10 · Updated 2026-09-10 · Limits: quantity estimation, not structural design or site supervision.