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Roof Pitch Calculator

Use this roof pitch calculator entirely in your browser.

ResultRoof pitch angle: 26.57°

Pitch ratio: 6.00 in 12

Slope length for the entered run: 13.42 units

Slope factor: 1.1180

This geometry does not size rafters, determine drainage, or establish structural or code compliance.

Calculations happen locally in your browser.

How to use this calculator

  1. Enter the labelled values and review the live result.
  2. Review the live result and use Copy result when you need to share it.

How the calculation works

The angle is arctangent of rise divided by run; Pythagoras gives the corresponding slope length.

Formula

Angle = arctan(rise ÷ run); slope length = √(rise² + run²)

Step-by-step calculation

  1. Enter the labelled values and review the live result.
  2. The angle is arctangent of rise divided by run; Pythagoras gives the corresponding slope length.
  3. Check the displayed result, then copy it if needed.

Worked example

A rise of 6 over a run of 12 produces a 26.57° angle and a 6-in-12 pitch.

Risk guidance

Consistent units are enough

Rise and run may be entered in any matching unit because the angle and ratio depend on their proportion. The slope length is returned in that same unit.

Geometry is not roof design

The result does not size rafters, calculate loads, select coverings, test drainage, or interpret construction requirements. Use project-specific design information.

Frequently asked questions

Does this tool send my inputs anywhere?

No. The interactive calculation runs in your browser and this site does not submit tool inputs to a backend.

How should I use the result?

Use it for early planning only. Verify measurements, definitions, current local requirements, and the complete design with the relevant authority and appropriately qualified professionals.

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