How to Measure Roof Pitch?

Roof pitch angle describes how steep one side of a roof is. It is based on the relationship between 2 measurements:

Run - the horizontal distance

Rise - the vertical height over the distance

Roof pitch can be expressed as a ratio (like 4:12) or converted into degrees (like 20 degrees) when required for calculators or for choosing the right roofing products.

Tools You Will Need:

Tape Measure

Spirit Level

Ladder or safe roof or loft access

Pen and paper or phone for making notes

Measure Roof Pitch Using Rise and Run

This is the most common and most accurate method of measuring roof angle.

Step 1: Measure the run

Place the spirit level horizontally against the roof slope, and measure a fixed horizontal distance. Common choices are 300mm or 12 inches.

This measurement is your run.

Step 2: Measure the rise:

From the end of the spirit level, measure vertically down to the roof surface.

This vertical distance is the rise.

Step 3: Calculate the pitch

You now have your roof pitch angle as a ratio - Rise: Run

For example, if the rise is 100mm over a 300mm run, the pitch is 1:3.

Convert Roof Angle to Degrees

Some roofing products and calculators require pitch to be entered in degrees rather than a ratio.

Once you have measured rise and run, you can convert this using a roof angle calculator. This removes the need for manual trigonometry and helps avoid errors.

You can calculate pitch in degrees using this tool:

https://www.metal-guttering.co.uk/ridges-valleys