Ramp slope calculator
Enter the rise and pick a slope to see the ramp length, percent grade, angle, and how many runs and landings it needs. We check the US ADA accessibility standard.
See your design as an AI render — free- Percent grade
- 8.33%
- Angle
- 4.76°
- Sloped length
- 24.08 ft
- Runs
- 1
- Intermediate landings
- 0
- Total length with landings
- 24 ft
- Passes · US — 2010 ADA §405: maximum slope 1:12 and no more than 30 in of rise per run
Quick reference only. Always check your country's and city's code before signing off a design.
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How to calculate a ramp
A 1:N slope tells you how many units of length the ramp needs for each unit of rise.
- 1
Measure the rise
It is the height difference between the bottom and the top of the ramp, finished floor to finished floor.
- 2
Multiply by the slope
Horizontal run = rise × N. 24 in at 1:12 needs 24 × 12 = 288 in, or 24 ft.
- 3
Turn it into percent and angle
Percent grade = 100 ÷ N: 1:12 is 8.33%. The angle is the arctangent of 1 ÷ N: 4.76°.
- 4
Split it into runs
The ADA limits each run to 30 in of rise and asks for landings at least 60 in long between them. The calculator adds those landings to the total length.
Common ramp slopes
Horizontal run for each foot (or meter) of rise. The bigger the N, the gentler and longer the ramp.
| Slope | Percent grade | Angle | Run per 1 ft of rise |
|---|---|---|---|
| 1:8 | 12.5% | 7.13° | 8 ft |
| 1:10 | 10% | 5.71° | 10 ft |
| 1:12 | 8.33% | 4.76° | 12 ft |
| 1:16 | 6.25% | 3.58° | 16 ft |
| 1:20 | 5% | 2.86° | 20 ft |
Frequently asked questions
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