# Roof Pitch Calculator

URL: https://speedycalculator.com/calculators/construction/roof-pitch/
Last updated: 2026-10-25

> The roof pitch calculator converts rise and run into roof pitch (x/12), angle in degrees, slope percentage and the pitch multiplier, and works backwards from any of them.

## Inputs

- Rise (in, cm, mm, ft, m)
- Run (in, cm, mm, ft, m)

## Results

- Pitch
- Angle
- Grade
- Pitch multiplier
- Rafter length for this rise and run

## Formula

```
Pitch = rise ÷ run × 12 (written x/12)
Angle = atan(rise ÷ run)
Grade = rise ÷ run × 100%
Multiplier = √(1 + (rise/run)²)
```

## Explanation

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

PitchAngleGradeMultiplier1/124.76°8.3%1.0032/129.46°16.7%1.0143/1214.04°25.0%1.0314/1218.43°33.3%1.0545/1222.62°41.7%1.0836/1226.57°50.0%1.1187/1230.26°58.3%1.1588/1233.69°66.7%1.2029/1236.87°75.0%1.25010/1239.81°83.3%1.30211/1242.51°91.7%1.35712/1245.00°100.0%1.41414/1249.40°116.7%1.53716/1253.13°133.3%1.66718/1256.31°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

FieldWhat to enterRiseUnits: in, cm, mm, ft, mRunUnits: 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)

## 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.

## FAQ

**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).