Roof Pitch Calculator

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.

Need to turn a measured horizontal run into its matching sloped length? Use the roof pitch multiplier and factor chart to calculate it and work backward once. To see the roof pitch formula calculate rise/run forward and reverse-check the same pair, start with matching measurement units.

To turn a centered gable's full span and pitch into a ridge-height check, use the roof peak calculator worksheet; it keeps full span, one-plane run, ridge height, and diagonal length on separate reference lines.

For one common check, the 4:12 pitch roof calculator starts with horizontal run, shows its matching rise, and keeps the resulting diagonal separate from framing or roof-covering decisions.

For any stated pitch, use the rafter pitch calculator to put the horizontal run, rise, and geometric diagonal in one labelled triangle before treating any result as a separate framing-layout question.

If your field notes use metric measurements, use the metric roof pitch worksheet to keep rise and horizontal run in the same unit before checking the result as x:12.

Have a first number but need to confirm it? The roof pitch estimator worksheet keeps an estimate separate from the measured rise/run pair that can verify or replace it.

For a one-plane shed roof, start with the two endpoint heights and the total horizontal run in the shed roof pitch calculator guide; keep framing cuts and roof-covering choices as separate checks.

A slope result is not a universal roof-system approval. Use the minimum roof slope guide to keep the measured geometry, named system, and governing project requirements together.

For a water-path check beneath the main covering, read what roof underlay can do—and what it cannot decide.

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.