BuildersMeasures

Roof Pitch Calculator

Calculate roof pitch, pitch percentage, roof angle, rise, run and slope length from your roof measurements. Enter the rise and run, or use the roof angle to estimate the required rise.

Calculate Roof Pitch

Vertical rise from the roof eave to the ridge.
Horizontal distance used to calculate the pitch.
For a gable or hip roof, enter the full building width.
Used to estimate one sloped roof surface area.
Roof Pitch -
Pitch Percentage -
Roof Angle -
Rise -
Run -
Sloped Roof Length -
Rise-to-Run Ratio -
Roof pitch format: A pitch of 6:12 means the roof rises 6 units for every 12 units of horizontal run. The same slope is also expressed as 50% grade.

What Is Roof Pitch?

Roof pitch describes how steep a roof is. It compares vertical rise with horizontal run. Builders commonly express roof pitch as a ratio such as 4:12, 6:12 or 12:12.

A 6:12 roof rises 6 inches for every 12 inches of horizontal run. A 12:12 roof has equal rise and run, producing a 45 deg roof angle.

How the Roof Pitch Calculator Works

Roof Pitch Ratio

The calculator divides the roof rise by the horizontal run. It then expresses the result using a common 12-unit run.

Pitch = Rise / Run

Pitch Percentage

Pitch percentage shows the slope as a percentage.

Pitch % = Rise / Run × 100

Roof Angle

The roof angle is calculated from the rise and run using the inverse tangent function.

Angle = arctan(Rise / Run)

Sloped Roof Length

The sloped length is the diagonal distance from the lower roof edge toward the ridge.

Sloped Length = square root of (Rise squared + Run squared)

Common Roof Pitch Examples

Pitch Pitch Percentage Approx. Angle Rise for 12 Run
2:12 16.67% 9.46 deg 2
3:12 25% 14.04 deg 3
4:12 33.33% 18.43 deg 4
5:12 41.67% 22.62 deg 5
6:12 50% 26.57 deg 6
7:12 58.33% 30.26 deg 7
8:12 66.67% 33.69 deg 8
9:12 75% 36.87 deg 9
10:12 83.33% 39.81 deg 10
11:12 91.67% 42.51 deg 11
12:12 100% 45 deg 12

Roof Pitch and Roof Design

Roof pitch affects drainage, roof height, rafter length, material coverage and the amount of roof surface exposed to weather.

The correct pitch depends on the roof system, climate, materials, structural design and local building requirements. A pitch calculator provides geometric measurements, not a structural roof design.

  • Low-slope roofs have a smaller rise compared with the run.
  • Steeper roofs have a larger rise compared with the run.
  • A 12:12 pitch has equal rise and run.
  • Roof angle and roof pitch are related but are not the same measurement.
  • Roofing material manufacturers often specify minimum roof slopes.

How to Measure Roof Pitch

For an existing roof, measure the horizontal run and vertical rise from a safe location such as the attic or roof framing. Avoid taking measurements from an unsafe roof surface.

For a simple gable roof, half of the building width is often used as the horizontal run when the ridge is centered. For a shed roof, the measured horizontal distance from the low edge to the high edge is used.

Roof Pitch FAQs

A 6:12 roof pitch means the roof rises 6 units vertically for every 12 units of horizontal run. Its pitch percentage is 50% and its approximate roof angle is 26.57 deg.
Divide the roof rise by the horizontal run. To express the result as a common pitch, multiply the decimal slope by 12. For example, a rise of 6 over a run of 12 produces a 6:12 pitch.
A 6:12 roof has an approximate angle of 26.57 deg.
A 12:12 roof rises 12 units for every 12 units of horizontal run. This equals a 100% pitch and an angle of 45 deg.
Yes. Divide rise by run and multiply by 100. For example, a 6:12 pitch equals 50%.
Roof pitch is one factor used to calculate the geometric slope length of a rafter. Actual rafter design also accounts for overhangs, ridge details, cuts, bearing points and structural requirements.
No. Roof pitch describes the relationship between rise and run, usually as a ratio such as 6:12. Roof angle expresses the slope in degrees.

This calculator provides geometric estimates for planning and measurement. Roofing installation and structural decisions should follow applicable building codes, manufacturer requirements and professional engineering or construction guidance.