Ramp Length Calculator: Slope Rules for 5 Countries

How the ramp length is calculated

Every rule uses the same arithmetic: minimum length equals the height divided by the maximum slope. A 15 cm step at 1:12 needs 15 × 12 = 180 cm of ramp. At 6% it needs 15 ÷ 0.06 = 250 cm. The difference between countries comes from the slope each rule allows and from the landings it adds.

Slope can be written as a ratio (1:12 means 1 unit of rise for every 12 units of length) or as a percentage (1:12 is about 8.3%). The calculator shows both, and it always rounds the length up to the next full centimetre so the result is never steeper than the rule.

How to measure the height

Measure straight up from the lower floor to the top of the step or threshold, at the point where the wheel will cross. If the ground slopes, measure at the lowest point where the ramp will start. Measure twice and use the larger number.

For a doorway with steps on both sides, measure each side separately: a ramp inside and a ramp outside are two calculations.

Use a tape measure held vertically, not along the slope.
Include any door sill or weather strip the wheels must cross.
Check that the space in front of the step is long enough for the ramp plus the landing.

Why the countries differ

The US ADA rule sets one maximum slope (1:12) and limits each run to 30 in of rise. Germany's DIN 18040-1 is stricter at 6%. The Dutch Bbl uses a sliding scale: very small height differences may be steeper, larger ones must be gentler. France sets 5% with tolerances for short ramps, and Spain's CTE allows steeper slopes for short ramps and gentler ones as the ramp gets longer.

All five rules are written for public or new buildings. They are useful reference points for a home, but a private home is usually not required to meet them, and a portable or threshold ramp follows its maker's own limits.

When a ramp is not the right answer

A long ramp needs space, landings and edge protection. If the result is longer than the space you have, a steeper ramp is not a safe shortcut for someone propelling their own wheelchair. Ask an occupational therapist or a home adaptation adviser about alternatives such as a platform lift, a different entrance or a threshold ramp for very small steps only.

Very small sills (a few centimetres) are often handled by a threshold ramp; see our threshold ramp guide.
Heights above about 1 m usually point to a lift rather than a ramp.
Wet, icy or outdoor ramps need a slip-resistant surface and regular checks.

Questions

How long should a ramp be for a 6 inch step?

Under the US ADA rule of 1:12, a 6 inch (15 cm) step needs a ramp at least 72 inches (183 cm) long, plus landings at the top and bottom. Germany's 6% rule would need 250 cm and France's 5% rule 300 cm, though France tolerates 8% for ramps up to 2 m long.

What is the maximum slope for a wheelchair ramp?

The US ADA Standards allow a maximum running slope of 1:12, about 8.3%. Germany's DIN 18040-1 allows 6%, France 5% with short-ramp tolerances, and Spain 10%, 8% or 6% depending on length. The Netherlands uses a scale from 1:6 for tiny height differences to 1:20 for up to 1 m.

Do these rules apply to my home?

Usually not directly. These rules are written for public buildings and new construction. They are good reference points for a safe slope at home, but your local rules, the ramp maker's instructions and advice from an occupational therapist matter more for a private home.

Is a steeper ramp acceptable with a helper?

Some portable ramp makers allow steeper slopes when a trained helper pushes the chair, but limits differ by product. Follow the maker's stated slope for the exact ramp, and remember that a steeper ramp is harder and riskier for anyone going up or down alone.

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