Roofing calculator
Pitch turns a footprint into real roof area. Squares and bundles come off that, not the ground plan.
Roofing
Pitch turns a footprint into real roof area. Squares and bundles come off that, not the ground plan.
A square is 100 sq ft of roof surface. Hips and valleys want 15 per cent, not 10.
$1,948
17.7 squares of three-tab asphalt at $110.00 / square
Free. No signup. The quantities carry over as line items.
How this roofing calculator works
The number that matters is roof surface, not the footprint you measured on the ground. Pitch is what turns one into the other, and it is the step most people skip.
The formula
squares = footprint × pitch multiplier ÷ 100 × (1 + waste) · bundles = squares × 3
Assumptions and defaults
| 4 / 12 pitch | 1.054× |
| 6 / 12 pitch | 1.118× |
| 8 / 12 pitch | 1.202× |
| 10 / 12 pitch | 1.302× |
| 12 / 12 pitch | 1.414× |
| Default waste | 10% |
Pro tips
Hips and valleys want fifteen per cent, not ten. Every valley is a cut on both sides and the offcuts are rarely long enough to use.
Order starter and ridge separately — they are not in the field bundle count and they are the two things crews run out of on the last afternoon.
A square is 100 sq ft of roof surface. Suppliers, estimators and crews all speak in squares, so quote in them too.
Common questions
How many squares is my roof?
Multiply footprint length by width, multiply by the pitch factor for your slope, and divide by 100. A 48 × 30 ranch at 6/12 comes to about 16 squares before waste.
How do I figure roof pitch?
Rise over 12 inches of run. Hold a level out a foot from the roof surface and measure down to the roof at the far end — that measurement in inches is your rise.
How many bundles of shingles per square?
Three for standard architectural and three-tab. Heavier designer shingles run four or five, so check the wrapper.
Does a steeper roof cost more to shingle?
Yes, twice over: more surface area for the same footprint, and slower, more careful work above about 7/12 where crews need staging.