Roof pitch calculator
Work out a roof's pitch in degrees (and as a ratio) from its rise and run — useful for tile/slate selection, which often specifies a minimum pitch.
Result
Roof pitch
Pitch ratio
How to use this tool
- Measure the vertical rise from wall plate to ridge, and the horizontal run (half the roof's span).
- Enter both measurements in metres.
- Read the pitch in degrees and as a ratio.
Assumptions
- Assumes a simple symmetrical gable roof; complex or asymmetric roofs need each slope measured separately.
Technical details: what the fields mean
- Rise
riseM - Vertical height gained from the wall plate to the ridge, in metres.
- Run
runM - Horizontal distance from the wall plate to directly under the ridge (half the total span), in metres.
Methodology
Pitch (degrees) = arctan(rise ÷ run). The ratio is normalized to 1 unit of rise, so it is written 1:run/rise (for example, 1:2 means 1 unit up for every 2 units across).
Worked example
2m rise over a 4m run
Inputs: Rise: 2 m, Run: 4 m
Result: 26.6° (approx. 1:2 ratio)
Practical guidance
- Most concrete/clay tiles need a minimum pitch (often 15–22.5° depending on the product) — check your chosen tile's manufacturer data sheet.
- Slate roofs can often go lower than tile roofs — again, check the specific product's minimum pitch.
Common mistakes
- Measuring run as the full roof span instead of half of it.
- Mixing metric and imperial measurements in the same calculation.
FAQs
What roof pitch is 2m rise over 4m run?
About 26.6 degrees, roughly a 1:2 pitch ratio.
What's the minimum pitch for roof tiles?
It depends entirely on the tile product — always check the manufacturer's minimum-pitch specification rather than assuming a generic figure.
Last reviewed: 2026-10-11
Does not check your result against any specific tile/slate manufacturer's minimum pitch requirement — verify separately.
This tool provides an indicative estimate, based on the assumptions stated above.
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