Convert between slope percentage, degrees, and rise/run ratio. Enter any one value and get all three formats instantly — useful for grading, drainage, ramps, and layout work.
Grade lasers and rotary lasers let you verify slope across a full work area in minutes. Shop slope and grade measurement tools at Express Tools.
Shop Express Tools →Slope, grade, pitch, gradient — all refer to the same measurement: the ratio of vertical rise to horizontal run. The conversion between formats uses basic trigonometry, but the key insight is that the relationship between percent grade and degrees is non-linear. A 45° slope is 100% grade (1:1), not 45%.
Contractors most commonly use percent grade (e.g., “2% slope for drainage”). Surveyors and civil engineers sometimes use rise:run ratios in the format X:Y. Machine control systems typically use percent. Roof framing uses pitch in the format X/12 (e.g., 4/12 pitch = 4 inches of rise per 12 inches of run = 33.3%). Pipe lasers use either percent or inches-per-foot depending on the brand. This calculator handles all formats.
| Grade % | Degrees | Ratio | In/Ft | Common Use |
|---|---|---|---|---|
| 0.5% | 0.29° | 1:200 | 0.06 in/ft | Minimum pipe grade (6") |
| 1.0% | 0.57° | 1:100 | 0.12 in/ft | Minimum paved drainage (IBC) |
| 2.0% | 1.15° | 1:50 | 0.24 in/ft | Standard paved drainage; ADA max cross-slope |
| 5.0% | 2.86° | 1:20 | 0.60 in/ft | ADA accessible ramp (preferred) |
| 8.33% | 4.76° | 1:12 | 1.00 in/ft | ADA max wheelchair ramp slope |
| 10% | 5.71° | 1:10 | 1.20 in/ft | Typical driveway max; highway ramp limit |
| 25% | 14.0° | 1:4 | 3.00 in/ft | Max slope stake (varies by soil) |
| 33.3% | 18.4° | 1:3 | 4.00 in/ft | Maximum fill slope for many soils |
| 100% | 45.0° | 1:1 | 12.0 in/ft | 45° angle; 1:1 slope |
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Start free trialTo convert slope percentage to degrees, divide the percentage by 100 to get the decimal slope, then take the arctangent. For example, 10% slope = arctan(0.10) = 5.71 degrees.
A 1:20 slope ratio means 1 unit of rise for every 20 units of run, which equals 5% grade (1 ÷ 20 × 100). This is a common slope for ADA-compliant ramps.
ADA guidelines require a maximum slope of 1:12 (8.33%) for wheelchair ramps, with a preferred slope of 1:20 (5%) or less for ease of use.
2% slope equals 0.24 inches per foot (2 ÷ 100 × 12). This is the standard minimum slope for surface drainage.