Slope and Rise [4.8.2]
Slope represents the proportion of vertical rise to horizontal length and can be represented as a ratio (as in ADAAG), percentage, pitch or in degrees.
| rise:length | percent | pitch | degree |
| 1:8 | 12.50% | .1250 | 7.13 |
| 1:10 | 10% | .1000 | 5.71 |
| 1:12 | 8.33% | .0833 | 4.76 |
| 1:13 | 7.69% | .0769 | 4.40 |
| 1:14 | 7.14% | .0714 | 4.09 |
| 1:15 | 6.67% | .0667 | 3.81 |
| 1:16 | 6.25% | .0625 | 3.58 |
| 1:17 | 5.88% | .0588 | 3.37 |
| 1:18 | 5.55% | .0555 | 3.18 |
| 1:19 | 5.26% | .0526 | 3.01 |
| 1:20 | 5.00% | .0500 | 2.86 |
| 1:50 | 2.00% | .0200 | 1.15 |
Slope and length greatly determine a ramp's usability. There are trade-offs between the two: a steeper slope makes the run shorter, while a more gradual slope increases the length. A maximum slope of 1:12 is specified although ADAAG calls for the "least possible" slope to encourage more gradual slopes which better serve children and people with limited stamina or upper body strength. A recent study by the Access Board ("Technical Requirements for Ramps" (1996) by the Center for Accessible Housing) indicates a significant increase in exertion occurs on ramps with slopes 1:14 or steeper. Recommendations: Consider slopes between 1:16 and 1:20 as preferred, especially at ramps with long runs. The slope should be consistent along the full length of the run. Variation above regular construction tolerances can be disruptive to wheelchair travel, especially in the ascent direction.
Alterations/ Historic Preservation
Steeper slopes are allowed for short ramps where a 1:12 slope is not technically feasible.
| Scope | Max Rise | Max Slope |
| altered facilities (including historic) | 3 in. | 1:8 |
| altered facilities (including historic) | 6 in. | 1:10 |
| qualified historic structures only | 4 in. | 1:6 |
Rise
The maximum length of a run is determined by the rise (30 inches maximum) and the slope:
| Max. Rise | Slope | Max. Length | Max. Rise | Slope | Max. Length |
| 30 in. | 1:12 | 30 ft | 30 in. | 1:16 | 40 ft |
| 30 in. | 1:13 | 32.5 ft | 30 in. | 1:17 | 42.5 ft |
| 30 in. | 1:14 | 35 ft | 30 in. | 1:18 | 45 ft. |
| 30 in. | 1:15 | 37.5 ft. | 30 in. | 1:19 | 47.5 ft |
The number of runs per ramp is not limited although the more runs a ramp has the less usable it is. While intermediate landings offer resting points, they do not reduce the amount of force people using wheelchairs must exert traveling up ramps.
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