how high should wheelchair ramps be
1 Maximum slope for hand-propelled wheelchair ramps should be 1 of rise to every 12 of length (4.8 degree angle; 8.3% grade). 2  Maximum slope for power chairs should be 1.5 rise to 12 length (7.1 degree angle; 12.5% grade). 3  Minimum width should be 36 (inside rails) - (48 is ideal).earn the correct measurements of a properly constructed wheelchair ramp: 1  Maximum slope for hand-propelled wheelchair ramps should be 1 of rise to every 12 of length (4.8 degree angle; 8.3% grade).