Roof pitch is the steepness of a roof, usually given as inches of rise per 12 inches of horizontal run (6/12, 8/12…) in North America and as an angle elsewhere. Pitch decides which roofing materials are allowed: asphalt shingles need at least 2/12 (with special underlayment below 4/12) while low-slope membranes handle flatter roofs.
How to use the Roof Pitch Calculator
- Rise
- Run
- Every result field is editable: type into Pitch or any other result and Rise plus every other field update to match.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the rise and the run you measured – for example with a level and tape on the rafter. The calculator returns pitch, angle, percentage and multiplier. Type into the pitch or angle to find the matching rise.
Pitch to angle
| Pitch | Angle | Grade | Multiplier |
|---|---|---|---|
| 1/12 | 4.76° | 8.3% | 1.003 |
| 2/12 | 9.46° | 16.7% | 1.014 |
| 3/12 | 14.04° | 25.0% | 1.031 |
| 4/12 | 18.43° | 33.3% | 1.054 |
| 5/12 | 22.62° | 41.7% | 1.083 |
| 6/12 | 26.57° | 50.0% | 1.118 |
| 7/12 | 30.26° | 58.3% | 1.158 |
| 8/12 | 33.69° | 66.7% | 1.202 |
| 9/12 | 36.87° | 75.0% | 1.250 |
| 10/12 | 39.81° | 83.3% | 1.302 |
| 11/12 | 42.51° | 91.7% | 1.357 |
| 12/12 | 45.00° | 100.0% | 1.414 |
| 14/12 | 49.40° | 116.7% | 1.537 |
| 16/12 | 53.13° | 133.3% | 1.667 |
| 18/12 | 56.31° | 150.0% | 1.803 |
Tips for an accurate estimate
- Measure the footprint from the ground and apply the pitch multiplier rather than climbing on the roof.
- Add 10% waste for simple gable roofs and 15–20% for hips, valleys and dormers.
- Confirm design snow and wind loads with your local building department before changing framing or roofing.
- Always work with fall protection; roofing is one of the most dangerous trades.
Common mistakes to avoid
- Using the footprint area instead of the sloped roof area when ordering materials.
- Forgetting starter strips, ridge caps, drip edge and underlayment.
- Mixing up pitch (rise per 12 in of run) with the roof angle in degrees.
Inputs explained
| Field | What to enter |
|---|---|
| Rise | Units: in, cm, mm, ft, m |
| Run | Units: in, cm, mm, ft, m |
What each result means
- Pitch = [Rise]÷[Run]×12
- Angle = deg(atan([Rise]÷[Run]))
- Grade = [Rise]÷[Run]×100
- Pitch multiplier = sqrt(1 + ([Rise]÷[Run])^2)
- Rafter length for this rise and run = sqrt([Rise]^2 + [Run]^2)
Formula
Pitch = rise ÷ run × 12 (written x/12)Angle = atan(rise ÷ run)Grade = rise ÷ run × 100%Multiplier = √(1 + (rise/run)²)Worked example
Inputs — Rise: 6 in; Run: 12 in.
Results — Pitch = 6 /12; Angle = 26.57 °; Grade = 50 %; Pitch multiplier = 1.118; Rafter length for this rise and run = 13.416 in.
Frequently asked questions
What is a 6/12 roof pitch in degrees?
26.57°. 4/12 is 18.43°, 8/12 is 33.69° and 12/12 is 45°.
What is the minimum pitch for shingles?
2/12 with double underlayment; 4/12 or more with standard underlayment.
How do I measure roof pitch?
Hold a level horizontally against the rafter, measure 12 in along it and measure down to the roof: that distance is the rise.
What formula does the Roof Pitch Calculator use?
Pitch = rise ÷ run × 12 (written x/12).