Free tool · No signup · Feet or metres
Roofing squares and pitch calculator
Turn the footprint and pitch of a roof into its true surface area, then into squares, bundles, underlayment, drip edge and ridge cap, or tiles and membrane if you work in metres.
How it works
- Pitch multiplier = √(1 + (rise ÷ 12)²) for a pitch in inches per 12, or 1 ÷ cos(angle) for a pitch in degrees.
- True roof area = plan area × pitch multiplier. Area with waste adds your waste percentage.
- Squares = area with waste ÷ 100. Bundles = squares × bundles per square, rounded up.
- Underlayment or membrane rolls = true area ÷ roll coverage, rounded up. Add more if your rolls need wide laps.
- Rafter length = run × pitch multiplier, before any overhang or ridge-board allowance.
Pitch multipliers
The common pitches, from a low 2/12 to a steep 12/12.
Three worked examples
Each was checked against a separate calculation. Enter the same numbers above and you will get the same results.
Example 1
Gable roof, 6/12, architectural shingles
Example 2
Steep 12/12 roof with hips
Example 3
Concrete tile roof in metres, 35°
Roofer spreadsheets
Now do it for every roof.
Five spreadsheets: quotes and invoices, a roof area calculator, a material list, a re-roof quote and a job profit tracker. Pick your country.
One payment. Download for 365 days; the files are yours to keep. Compare the countries.
Questions
How do I convert a plan area to roof area?
Multiply the plan (footprint) area by the pitch multiplier. For a 6/12 pitch the multiplier is 1.118, so 2,000 sq ft of plan becomes 2,236 sq ft of roof surface.
What is a roofing square?
100 square feet of roof surface. Most shingles come three bundles to the square, so a 24.6-square roof needs 74 bundles once rounded up.
How do I find the pitch?
Measure how many inches the roof rises over 12 inches of level run, for example with a level and tape on a rafter or in the attic. In metric, use the angle in degrees from the plans or an angle finder.
Does the pitch multiplier work for hip roofs?
Yes for the roof area: every plane of a roof with one pitch rises at the same rate, so plan area times the multiplier gives the surface area. Hip and valley lengths themselves are longer than common rafters, so measure them for ridge cap and valley materials.
Is the result exact?
It is as exact as your measurements. The calculator rounds materials up to whole bundles, rolls and pieces; always check the coverage printed on the products you buy.