Guide to size
Government guidelines for fixed concrete ramps would generally use a gradient of 1 in 12 - e.g. a 3" height would require a 36" ramp length.
However, this is a guideline, and not a legal requirement. If space permits, this is the ideal guide, but unfortunately, the height is often too high to allow such a length - particularly on narrow footpaths etc.
Where only occasional use is required we have found that with a portable ramp, for powered scooters / electric wheelchairs (or a manual wheelchair with assistance) a gradient of 1 in 6 is adequate. (eg - a 6" step requires a 36" ramp).