Roofing Calculator
Free roofing calculator that converts your roof footprint and pitch into roofing squares, shingle bundles, and estimated cost. Works as a roof pitch calculator and roof square footage calculator for shingle jobs.
Calculate roofing squares
How the roofing calculator works
A roof is bigger than the ground it covers because it slopes. This roofing calculator first finds your true roof area, then expresses it in squares. Enter the footprint and the pitch, and the built-in roof pitch calculator computes a pitch factor — for a 6/12 roof that factor is about 1.118. Multiply a 1,500 sq ft footprint by 1.118 and you get roughly 1,677 sq ft of actual roof, or about 16.8 roofing squares before waste.
Because one square equals 100 sq ft, the tool also works as a roof square footage calculator and a roofing square calculator: it is simply area ÷ 100. A roof slope calculator uses the same pitch factor whether you describe slope as 4/12, 6/12, or 12/12.
Pitch factors and waste
Steeper roofs need more material. The roof slope calculator applies these common pitch factors so you do not have to: a low 4/12 slope multiplies the footprint by about 1.054, a 6/12 by 1.118, and a steep 12/12 by 1.414. Add 10% waste for a clean gable roof and 15% for hips, valleys, and dormers, since more cuts mean more offcuts.
How to use this calculator
- Measure the roof footprint. This roofing calculator starts with the footprint: the length × width the building covers at ground level, in square feet. For an L-shaped home, add the rectangles together.
- Find your pitch with the roof pitch calculator. Enter rise per 12 inches of run. The built-in roof pitch calculator converts that to a pitch factor — sqrt(rise² + 144) ÷ 12 — which a roof slope calculator uses to scale the flat footprint up to the true sloped surface.
- Convert area to roofing squares. The roof square footage calculator multiplies footprint by the pitch factor, then divides by 100. One roofing square equals 100 sq ft, the unit shingles are sold in, so this doubles as a roofing square calculator.
- Add waste and price the job. Add 10% waste for simple roofs or 15% for cut-up roofs with valleys and dormers. Enter a price per square to estimate shingle material cost.
Frequently asked questions
What is a roofing square?
A roofing square equals 100 square feet of roof surface. Shingles, underlayment, and labor are all priced by the square, which is why this roofing calculator reports squares rather than raw square feet.
How does the roof pitch calculator turn pitch into a factor?
It uses sqrt(rise² + 12²) ÷ 12. A 6/12 pitch gives sqrt(36 + 144) ÷ 12 ≈ 1.118, meaning the sloped roof is about 11.8% larger than the footprint.
Can I use this as a roof square footage calculator?
Yes. The actual roof area in square feet equals footprint × pitch factor, and squares are that area divided by 100, so the same tool gives you both numbers.
How much waste should I add?
Add 10% for a simple gable roof and 15% for complex roofs with multiple valleys, hips, or dormers where offcuts pile up.
Why is roofing such a high-value search?
Roofing jobs are expensive, so accurate roof slope calculator estimates help homeowners compare contractor bids and avoid ordering too few or too many shingles.
Squares by footprint and pitch
| Footprint | Pitch | Roofing squares |
|---|---|---|
| 1,500 sq ft | 6/12 | ~16.8 squares |
| 2,000 sq ft | 6/12 | ~22.4 squares |
| 2,000 sq ft | 12/12 | ~28.3 squares |
Shingles ship three bundles to a square, so multiply squares by three to get bundle count.