ROOFING GEOMETRY

Roof Pitch Calculator

Enter the vertical rise and horizontal run in the same unit.

RESULTS

Your roof slope

Pitch ratio6:12rise per 12 units of run

Roof angle26.565°degrees from horizontal

Slope50%rise ÷ run × 100

Rafter factor1.118rafter length ÷ run

How to calculate roof pitch

Roof pitch is the vertical rise compared with the horizontal run. This calculator expresses the same slope as a pitch ratio, an angle, a percentage, and a rafter factor.

pitch = (rise ÷ run) × 12standard X:12 notation

angle = atan(rise ÷ run)converted to degrees

slope = (rise ÷ run) × 100percentage grade

factor = √(rise² + run²) ÷ runsloped length per unit of run

Measurement notes

Use a vertical rise and a horizontal run measured in matching units. The units can be inches, feet, millimetres, or any other consistent length unit; the ratio does not change when both measurements use the same unit.

This is a geometry calculator for slope and estimating rafter length. It does not size structural members, account for irregular roof sections, or replace local building-code and manufacturer requirements.

Roof pitch calculator FAQ

Is roof pitch the same as roof slope?

They describe the same rise-over-run geometry here. The calculator shows it in the familiar X:12 pitch format and in other equivalent forms.

What is a roof pitch angle calculator?

It converts the rise/run ratio into the angle between the roof surface and the horizontal plane.

Can I use feet instead of inches?

Yes. Enter rise and run using the same unit. Because the calculation uses a ratio, matching units are what matter.