How to measure your roof

Every roofing price starts with one number: the roof's surface area. It is bigger than your house's footprint, because the roof is sloped — and the steeper it is, the bigger the difference. You do not need to climb anything to estimate it.

Step 1 — the footprint

Take your home's floor area and divide by the number of stories: a 1,800 sq ft two-storey home has roughly a 900 sq ft footprint. Add garage and porch roofs if they will be replaced too.

Step 2 — the pitch factor

Multiply the footprint by the factor for your pitch (the rise over a 12-inch run):

Pitch can be measured from the ground with a phone level app against a gable end, or from an attic rafter — never by walking a roof you are not equipped for.

Step 3 — sanity-check against "squares"

Roofers price in squares: 1 square = 100 sq ft of roof surface. A 2,000 sq ft roof is 20 squares. If a quote's square count differs from your estimate by more than ~10%, ask how it was measured — satellite measurement reports (which most roofers use) settle the question quickly, and a reputable contractor will show you one.

Tools that make measuring easier

Everything above works with a tape measure and a phone. These inexpensive tools make it faster — and keep you off the roof. The links below go to Amazon and are affiliate links: if you buy through one we may earn a commission at no extra cost to you (see our affiliate disclosure).

• Laser distance measurer — footprint dimensions from the ground, no ladder needed.
• Digital angle finder — reads the pitch off a gable end or an attic rafter.
• 100 ft tape measure — for eaves, rakes and porch roofs.
• Roof safety harness kit — only relevant if you are trained and equipped to go up; most homeowners should stay on the ground.

Try it