How to Measure a Roof for Shingles

Intermediate · 1–2 hours to measure

You don't need to crawl across a roof to estimate it. The actual roof area is just the building's footprint multiplied by a pitch factor that accounts for the slope — and roofers price everything in 'squares' (100 sq ft each). This guide shows how to measure the footprint from the ground, find the pitch safely, and convert it all into squares and shingle bundles for ordering. Safety first: any time you're on a roof, use proper fall protection.

What you'll need

• Tape measure or measuring wheel for the footprint
• A level and a ruler (or a pitch/speed-square app) to find the slope
• The roofing calculator to convert footprint + pitch into squares
• Pencil and paper, or a sketch of the roof plan
• For on-roof measuring: a stable ladder, soft-soled shoes, and a harness

Steps

1. 1

   Measure the footprint

   From the ground, measure the length and width of the building's outline, including any overhangs the roof covers. For complex roofs, break the plan into rectangles and measure each.

2. 2

   Find the roof pitch

   Pitch is the rise over a 12 in run. Hold a level horizontal against a rafter or gable, measure up 12 in along it, then measure straight down to the roof — that drop is your rise (e.g. a 6 in drop = 6/12 pitch). A speed square or phone app works too.

3. 3

   Apply the pitch multiplier

   A sloped roof has more surface than its flat footprint. Multiply the footprint area by the pitch factor (about 1.05 for 4/12, 1.12 for 6/12, 1.20 for 8/12) to get true roof area — the calculator has these built in.

4. 4

   Convert to squares

   Divide the true roof area by 100 to get roofing squares, the unit roofers and suppliers quote in.

5. 5

   Figure bundles and waste

   Most architectural shingles come three bundles to the square. Add about 10% for waste, plus extra for hip-and-ridge caps and starter strips along eaves.

6. 6

   Add the accessories

   Don't forget underlayment (rolls by the square), drip edge for the perimeter, valley flashing, and a box of roofing nails per square or two.

Pro tips

• The roofing calculator turns footprint + pitch straight into squares and bundle count — no rooftop trip required.
• Measure the footprint from the ground whenever you can. The pitch multiplier does the rest, and it's far safer than walking a steep roof.
• Order full bundles and round up — running a single bundle short can mean a mismatched dye lot or a stalled job.
• Steeper roofs need more shingles for the same footprint and are harder to walk, so price the labor accordingly.

FAQ

Ready to estimate materials? Use the Roofing Squares Calculator →