The Americans with Disabilities Act requires wheelchair ramps to have a one to 12 ramp-to-slope ratio maximum and flat 5-foot by 5-foot platforms at the ramp's top and bottom, as of March 2015. Wheelchair ramp requirements vary based on the area.
The ADA's maximum ramp length before a turn or rest platform is 30 feet. The sides of a ramp must have handrails that are between 34 and 38 inches high. The minimum ramp width is 36 inches, except in California and Massachusetts, where it's 48 inches. Ramp requirements typically only apply to businesses and don't have to be met by residences. Residential wheelchair ramps may be governed by building codes.
Other countries have different governing bodies that set ramp regulations. In the United Kingdom, the Disability Discrimination Act regulates ramps.
A one to 12 ramp to slope ratio maximum is used in multiple countries. At that ratio, there is 1 foot of ramp for each inch the ramp rises.
If there isn't space for a long enough ramp, a U-shaped ramp may be used. These ramps have a turn platform that allows a person to make a U-turn. Since both sections of the ramp are next to each other, the ramp takes up less space.