UK gradient standards and ratios
In the UK, road signs and civil engineering plans traditionally express gradients as a ratio of 1 vertical unit to X horizontal units, written as "1 in X" (e.g. 1 in 10 for a 10% steep road hill).
UK Building Regulations Part M (Access to and use of buildings) specifies maximum ramp gradients: ramps steeper than 1 in 12 are not permitted, and slopes of 1 in 20 or shallower are preferred for wheelchair access.
This calculator provides the exact 1 in X ratio, percentage grade, angle in degrees, and ramp surface length.
Worked example: UK wheelchair ramp
For a doorstep rise of 300 mm (0.3 m) with a ramp run of 4.5 m:
Slope = 0.3 ÷ 4.5 = 0.0667. Ratio = 1 in 15 (compliant with UK Part M limits for ramps under 5m).
Gradient = 6.67% with an incline angle of 3.81°.
Inputs for the UK gradient calculator
Rise and Run
Enter vertical rise and horizontal run in metres or millimetres.
CALCULATOR QUESTIONS
UK gradient & road incline calculator questions
What does a "1 in 8" road sign mean in the UK?
A 1 in 8 sign warns of a steep hill where the road rises or falls by 1 metre for every 8 metres of horizontal distance (a 12.5% gradient).
What is the maximum ramp gradient under UK Building Regulations Part M?
Part M allows a maximum gradient of 1 in 12 for ramps up to 2 metres long, 1 in 15 for ramps up to 5 metres, and 1 in 20 for ramps up to 10 metres.