Slope Grade Calculator
Calculate slope ratio, grade percentage, angle, and slope length from a rise and run, and see how it compares to common ramp, roof, road, and driveway slope standards.
Input
Purely cosmetic — rise and run must already share the same unit.
Output
| Property | Value |
|---|---|
| No data yet | |
| Standard | Grade (%) | Your Slope |
|---|---|---|
| No data yet | ||
How your slope compares to a few widely used real-world slope benchmarks.
Guides
The Slope Grade Calculator converts a rise and run into every common way a slope gets described — a simplified ratio (like "1 : 12"), a grade percentage, an angle in degrees, and the actual slope length (the hypotenuse). It also shows how your slope compares against a handful of everyday real-world benchmarks: ADA ramps, driveways, highways, and low-slope roofs.
How to use it
- Enter the rise — the vertical change in height.
- Enter the run — the horizontal distance it happens over.
- Pick a unit if you'd like it labeled in the output (it's purely cosmetic — rise and run just need to already share the same unit).
The ratio, grade percentage, angle, and slope length appear instantly, along with a comparison table showing whether your slope is steeper or gentler than common reference slopes.
The math
- Grade (%) =
rise ÷ run × 100 - Angle =
atan(rise ÷ run), converted from radians to degrees - Slope Ratio is rise and run reduced so the rise side is 1 — a "1 : 12" ramp rises 1 unit for every 12 units of run
- Slope Length =
√(rise² + run²)— the actual distance along the sloped surface, always a bit longer than the run
For example, a wheelchair ramp rising 4 inches over a 48-inch run has a grade of 4 ÷ 48 × 100 = 8.33%, a ratio of 1 : 12, an angle of about 4.76°, and a slope length of about 48.17 inches.
What's a "good" slope?
It depends entirely on what the slope is for. A few widely used benchmarks:
| Standard | Grade |
|---|---|
| ADA accessible ramp (max) | 8.33% (1 : 12) |
| Recommended wheelchair ramp | 6.25% (1 : 16) |
| Typical driveway (max) | 12% |
| Highway (max grade) | 6% |
| Low-slope roof (min for drainage) | 16.7% (2 : 12) |
Does rise and run need to be in feet?
No — any consistent unit works (inches, meters, whatever you measured in), since the ratio and percentage are unitless. The unit selector only labels the slope length in the result table.
For a broader right-triangle solve (all three sides and angles from any two known values), use the Triangle Calculator. To convert an angle to other units, use the Angle Converter.
Everything runs in your browser; no inputs are sent to a server.
Use it from code
From 3 credits per callREST API
curl -X POST https://api.iotools.cloud/v1/tool/slope-grade-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"rise": "4",
"run": "48",
"unit": "in"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `slope-grade-calculator` tool (Slope Grade Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.