BuildProjectCalc
Roofing

Roof Pitch Calculator

Calculate objective roof geometry from rise and run, including pitch per 12 inches, slope percentage, and angle in degrees.

Project measurements

Enter rise and run in the same unit. The result is geometric only and is not structural or safety guidance.

Vertical change
Horizontal distance

How to use this calculator

  1. Measure the vertical rise and horizontal run using the same unit.
  2. Enter both values.
  3. Calculate to see pitch per 12 units, slope percentage, and angle.

How the calculation works

Pitch per 12 scales the rise-to-run ratio to a 12-unit run. Slope percentage is rise divided by run times 100. The angle is the arctangent of rise divided by run.

Formula

Pitch = (rise ÷ run) × 12
Slope % = (rise ÷ run) × 100
Angle = arctan(rise ÷ run)

Worked example

A rise of 6 and run of 12 produces a 6:12 pitch, a 50% slope, and an angle of approximately 26.6°.

Project considerations

  • Use matching units for rise and run.
  • This calculation describes geometry only.
  • Roof access is hazardous; use safe measurement methods and qualified help when needed.

Frequently asked questions

What does a 6:12 pitch mean?

The roof rises 6 units for every 12 units of horizontal run.

Is roof pitch the same as roof angle?

They describe the same slope differently. Pitch is a rise-to-run ratio, while angle is measured in degrees.