Grade and Slope Converter
Convert slope between percentage grade, degrees, ratio (1:x), and rise-over-run.
Used for road grading, roof pitch, ramps, treadmills, and accessibility ramps.
Type in any field and the others update instantly, roof pitch included.
Slope can be expressed in several equivalent ways.
Conversion formulas:
- Slope % = (Rise / Run) × 100
- Slope degrees = arctan(Rise / Run)
- Slope ratio 1:X = 1 : (Run / Rise)
- Rise/Run = tan(degrees)
Relationship between units:
| Degrees | Percent | Ratio | Description |
|---|---|---|---|
| 1° | 1.75% | 1:57.3 | Nearly flat |
| 5° | 8.75% | 1:11.4 | Gentle slope |
| 10° | 17.6% | 1:5.7 | Moderate slope |
| 15° | 26.8% | 1:3.7 | Steep slope |
| 30° | 57.7% | 1:1.7 | Very steep |
| 45° | 100% | 1:1 | Equal rise & run |
Common references:
- Wheelchair ramp (ADA): max 8.3% (1:12, 4.76°)
- Steep road: 8-12% (4.6-6.8°)
- Steep hiking trail: 20-40% (11-22°)
- Roof pitch 4:12: 33.3% (18.4°)
- Staircase: 60-70% (31-35°)
The thing that surprises everyone is that a 100% grade is not vertical, it’s 45 degrees. Percent grade is rise over run, so 100% means you climb one unit for every one you travel forward, which is exactly 45 degrees; a truly vertical wall would be infinite percent. It’s also why a “10% grade” road sign sounds gentler than it feels: 10% is only about 5.7 degrees, but it’s steep enough to cook your brakes on a long descent.
Different fields prefer different forms of the same number. Roads and treadmills use percent, wheelchair ramps and railways use ratios like 1:12, and roofers use “pitch” written as rise per 12 inches of run. They all describe the same steepness, which is why converting between them matters whenever a spec and a tool disagree, such as reading a ramp code given as a ratio while your phone’s level reads degrees.
Roof pitch, since it is the one written back to front. A roofer says “four twelve” and means 4 inches of rise for every 12 inches of horizontal run, so the second number is always 12 and only the first one changes. Divide the first by 12 and you have the plain slope.
| Pitch | Percent | Degrees | Notes |
|---|---|---|---|
| 2:12 | 16.7% | 9.5° | Too shallow for most shingles, needs a membrane |
| 3:12 | 25.0% | 14.0° | The usual minimum for asphalt shingles |
| 4:12 | 33.3% | 18.4° | The common residential pitch |
| 6:12 | 50.0% | 26.6° | Walkable, but the last one that is |
| 8:12 | 66.7% | 33.7° | Roof jacks or staging territory |
| 12:12 | 100% | 45.0° | A dead 45, and steeper than it sounds |
The reason the two shallow rows matter is that shingle manufacturers void the warranty below 2:12 and require doubled underlayment between 2:12 and 4:12. A roof that measures 2.5:12 is not a judgment call, it is a different installation.
How we build and check this converter
This converter runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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