Roof Pitch Calculator
Calculate roof pitch from rise and run, convert between pitch, degrees and slope percentage, and get the pitch multiplier for estimating shingles and roofing materials.
Vertical rise over the run below
Use 12 to enter pitch directly
Flat plan area — we'll convert it to actual roof surface
Enter a footprint area to get actual roof surface area.
You might also need:Rafter Calculator·Stair Calculator
Understanding roof pitch
degrees = atan(rise ÷ run) · multiplier = √(rise² + run²) ÷ run
US roofers quote slope as rise over a 12-inch run. To estimate materials you need the pitch multiplier — the factor stretching flat footprint into sloped surface. Steeper roofs have dramatically more surface: a 12/12 roof has 41% more area to cover than its footprint.
Pitch conversion table
| Pitch | Degrees | Multiplier | Notes |
|---|---|---|---|
| 2/12 | 9.5° | 1.014 | Shingle minimum (special underlayment) |
| 4/12 | 18.4° | 1.054 | Common low-slope ranch |
| 6/12 | 26.6° | 1.118 | Most common US pitch |
| 8/12 | 33.7° | 1.202 | Steep — toe boards needed |
| 10/12 | 39.8° | 1.302 | Professional territory |
| 12/12 | 45° | 1.414 | A-frames, dormers |
Estimating shingles from pitch
Multiply your home's footprint (including eave overhangs) by the pitch multiplier to get roof area, divide by 100 for roofing "squares", then add 10–15% for ridge caps, starter strips and waste. Cutting new rafters instead? Therafter calculator uses this same geometry to give you rafter lengths, and the board foot calculator totals the lumber order.
Frequently asked questions
What does a 4/12 roof pitch mean?+
A 4/12 pitch rises 4 inches vertically for every 12 inches of horizontal run — about 18.4°. The first number is always the rise per 12 inches of run, which is how framers and roofers quote slope.
How do I measure my roof pitch?+
From inside the attic: hold a level horizontally against a rafter, mark 12 inches along the level, and measure vertically from that mark up to the rafter — that vertical distance in inches is your pitch. A smartphone level app held on the roof surface gives you degrees to convert.
What is the minimum pitch for shingles?+
Standard asphalt shingles require at least a 2/12 pitch, and between 2/12 and 4/12 they need special underlayment. Below 2/12 you need a membrane or metal system designed for low slopes.
What is a roof pitch multiplier?+
The pitch multiplier converts flat plan area to actual sloped roof area: multiply the footprint by it. A 6/12 roof has a multiplier of 1.118, so a 1,000 sq ft footprint has about 1,118 sq ft of roof surface to shingle.
What roof pitch is walkable?+
Most roofers consider up to 6/12 (26.6°) comfortably walkable, 7/12–9/12 walkable with care and toe boards, and 10/12+ (40°+) a job for staging, harnesses and professionals.