Ramp Calculator — Wheelchair Access & Gradient

This calculator sizes an access ramp to UK Building Regulations Part M Volume 2 (Access to buildings other than dwellings) and Part K (Protection from falling). You choose the target gradient — AD M 1.20 requires gradients to be "as shallow as practicable", so the gentlest gradient that fits your site is preferred but never the only compliant option.

Gradient limits (AD M Vol 2 Table 1 / AD K Diagram 2.1)

The maximum gradient depends on the going (length) of each flight, not the rise:

• Going up to 2m: maximum gradient 1:12
• Going up to 5m: maximum gradient 1:15
• Going up to 10m: maximum gradient 1:20
• Between 2m and 10m: interpolate (e.g. 1:14 for 4m, 1:19 for 9m)

No single flight may rise more than 500mm or have a going greater than 10m (AD M 1.26c), and each gradient's going limit gives its own maximum rise per flight: 500mm at 1:20, 333mm at 1:15 and 166mm at 1:12. Tall ramps are therefore split into flights with intermediate landings — more flights at steeper gradients.

Slope as an angle or percentage

UK regulations specify ramp slope as a gradient ratio, but the same slope can be written as an angle or a percentage. The three permitted gradients convert as follows:

• 1:20 ≈ 2.9° ≈ 5% (gentlest, recommended)
• 1:15 ≈ 3.8° ≈ 6.67%
• 1:12 ≈ 4.8° ≈ 8.33% (steepest permitted, short flights only)

The slope angle is calculated as arctan(1 ÷ gradient ratio), and the calculator shows this figure for whichever gradient you select — useful when a drawing specifies the disabled-access ramp slope in degrees rather than as a ratio.

Key requirements

• Minimum width: 1500mm between walls/upstands/kerbs for non-dwelling access ramps (AD K 2.9a / AD M 1.26e). 1200mm only applies to dwelling ramps (AD M Vol 1).
• Landings: foot & head landings ≥1200mm (AD M 1.26h / AD K 2.13a); intermediate landings ≥1500mm (AD M 1.26i / AD K 2.13b)
• Handrails: both sides at 900-1000mm height, extending 300mm past each end (AD M 1.26l, 1.37d). Dwelling ramps ≤600mm rise are exempt (AD K 2.12c).
• Steps in addition: required when the rise exceeds 300mm (AD M 1.26n / AD K 2.6a); a lift or alternative access is required when the total rise exceeds 2m (AD M 1.26d)
• Surface: must be firm, durable, slip-resistant and contrast visually with the landings

The slope length is calculated as rise × gradient ratio. For example, a 150mm rise at 1:12 = 0.15 × 12 = 1.8m. A 600mm rise gives a slope of 12.0m at 1:20 (or 9.0m at 1:15, 7.2m at 1:12). At 1:20 it splits into two flights (max 500mm each) with one 1.5m intermediate landing; at 1:12 the same rise needs four flights (max 166mm each) with three intermediate landings.