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

994.37 ft²

True roof area994.37 ft²
Roofing squares (100 sq ft)9.94 squares
Floor plan area861.113 ft²
Pitch factor1.15

Use my prices

Your prices per language/currency. Used when you enable “Use my prices” in calculators. My prices →

Calculate labour, margin & VAT

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

Add labour, overhead and your margin, and generate the professional PDF.

Create quote Calculate margin & VAT

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.