Start with the pitch
Almost every roofing number depends on pitch. Find it with the roof pitch calculator, then use the roofing squares calculator to turn your house footprint into true roof area, and the shingle calculator to order bundles.
Measure safely
You can measure pitch from inside the attic on a rafter, or from a ladder at the gable end. OSHA treats any roof steeper than 4/12 as a steep roof, and most people should not walk one steeper than about 6/12. The roof pitch chart lists every common pitch.
Which calculator should I use?
| You want to | Start here | What you get |
|---|---|---|
| Convert a pitch like 6/12 to degrees | Roof pitch calculator | Angle, slope percent and multiplier |
| Find the length of the roof surface | Roof area calculator | Area in square feet and squares for gable, hip or shed roofs |
| Convert square feet to roofing squares | Roofing squares calculator | Squares with waste |
| Order shingles | Shingle calculator | Bundles at 3 per square |
| Cut rafters | Rafter length calculator | Rafter length from span and pitch |
Common pitches at a glance
Pitch is the rise in inches for every 12 inches of run. The multiplier turns a footprint into roof area.
| Pitch | Angle | Slope | Multiplier |
|---|---|---|---|
| 3/12 | 14.0° | 25% | 1.031 |
| 4/12 | 18.4° | 33% | 1.054 |
| 5/12 | 22.6° | 42% | 1.083 |
| 6/12 | 26.6° | 50% | 1.118 |
| 7/12 | 30.3° | 58% | 1.158 |
| 8/12 | 33.7° | 67% | 1.202 |
| 9/12 | 36.9° | 75% | 1.250 |
| 10/12 | 39.8° | 83% | 1.302 |
| 12/12 | 45.0° | 100% | 1.414 |
The roof pitch chart and the degrees chart go further, and how to measure roof pitch shows how to find yours.
Safety and codes
These pages give geometry and typical product guidance. Roof work is dangerous, and shingle and metal roof makers set their own minimum pitches and install rules, which your local code may add to. Read the manufacturer's instructions for your product before you buy.
Who runs this site
RoofRatio is published by Hassan Nawaz. The formulas are shown on each page and sources are listed where a page relies on them. How pages are checked is described in the editorial policy. If a number looks wrong, use the contact page and say which page and what you expected.