The Americans with Disabilities Act limits ramp slopes to 1:12 (one inch of rise per foot of run) with no single run rising more than 30 in, after which a level 60-in landing is required. Gentler slopes of 1:16 or 1:20 are easier for manual wheelchair users. Assisted wheelchairs, scooters and loading ramps can be steeper.
How to use the Ramp Calculator
- Total rise
- Application / slope
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the total rise and choose the application (slope). The calculator returns the horizontal run, the ramp surface length, the angle and grade, the number of landings and the total length including landings.
Slopes compared
| Slope | Grade | Angle | Run per inch of rise |
|---|---|---|---|
| 1:12 | 8.3% | 4.76° | 12 in |
| 1:16 | 6.2% | 3.58° | 16 in |
| 1:20 | 5.0% | 2.86° | 20 in |
| 1:6 | 16.7% | 9.46° | 6 in |
| 1:8 | 12.5% | 7.13° | 8 in |
| 1:4 | 25.0% | 14.04° | 4 in |
Tips for an accurate estimate
- Take measurements at floor level and at the ceiling – walls and rooms are often slightly out of square.
- Use the manufacturer’s coverage, spacing and installation data when it differs from the typical values here.
- Keep a little extra of every finish material for touch-ups and repairs later.
- Check local building codes and permits before structural, electrical, plumbing or gas work.
Common mistakes to avoid
- Sizing heating or cooling equipment by area alone when insulation, windows and climate make a big difference.
- Buying too little paint, stain or flooring and ending up with mismatched batches.
- Overlooking the extra material for steps, railings, gables and trim.
Inputs explained
| Field | What to enter |
|---|---|
| Total rise | Units: in, cm, mm, ft, m |
| Application / slope | Choose one: ADA / commercial 1:12 (8.3%), Comfortable 1:16 (6.25%), Gentle 1:20 (5%), Residential, assisted wheelchair 2:12 (1:6) … |
What each result means
- Horizontal run = [Total rise]×[Application ÷ slope]
- Ramp length (surface) = sqrt([Total rise]^2 + [Horizontal run]^2)
- Angle = deg(atan(1÷[Application ÷ slope]))
- Grade = 100÷[Application ÷ slope]
- Intermediate landings (30 in max rise per run) = max(ceil([Total rise]÷0.762 – 0.000001) – 1, 0)
- Total length incl. 60 in landings = [Horizontal run] + [Intermediate landings (30 in max rise per run)]×1.524
Formula
Run = rise × slope ratio (e.g. 12 for 1:12)Ramp length = √(rise² + run²); angle = atan(1 ÷ ratio)Landings (ADA) = ceil(rise ÷ 30 in) − 1, each 60 in longWorked example
Inputs — Total rise: 24 in; Application / slope: ADA / commercial 1:12 (8.3%).
Results — Horizontal run = 24 ft; Ramp length (surface) = 24.08 ft; Angle = 4.76 °; Grade = 8.33 %; Intermediate landings (30 in max rise per run) = 0; Total length incl. 60 in landings = 24 ft.
Frequently asked questions
How long should a wheelchair ramp be?
At ADA 1:12, 1 ft of ramp per inch of rise – a 24 in rise needs a 24 ft run.
What is the maximum slope for a wheelchair ramp?
1:12 (8.33%, 4.76°) for new ADA construction; 1:16–1:20 is easier to use.
When do I need a landing?
ADA requires a 60 in level landing at the top, bottom and every 30 in of rise.
What formula does the Ramp Calculator use?
Run = rise × slope ratio (e.g. 12 for 1:12).