Elevation grade calculator
A rise of 1 over a run of 12 is an 8.333 % grade, an angle of about 4.76 degrees: the classic wheelchair-ramp slope. Enter the height change and the horizontal distance for a ramp, driveway or road profile. Free in your browser.
- Free
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- No sign-up
- Your data stays on your device
Run — free
Worked example
- Rise
- 1
- Run
- 12
- Percent grade
- 8.3333333333
- Ratio
- 0.0833333333
- Angle deg
- 4.7636416907
- Direction
- uphill
Elevation grade is the steepness of the ground between two stations, measured from a vertical rise and a strictly horizontal run. Civil designers, ramp builders, surveyors, and inspectors need that number as a percent, as a rise-over-run ratio, and as an angle in degrees before they pour a driveway, stamp a road profile, or set a wheelchair ramp. This elevation grade calculator accepts those two lengths in any shared linear unit, divides rise by run, multiplies by one hundred for the percent grade, keeps the decimal ratio, and takes the arctangent of that ratio for the slope angle.
How percent grade, ratio and angle follow from rise and run
Elevation grade is the ratio of vertical change to horizontal distance, not the slope length along the walking surface. If you climb a rise R over a horizontal run L, the decimal ratio is R divided by L, the percent grade is one hundred times that ratio, and the slope angle in degrees is the arctangent of that ratio converted from radians. Those three numbers describe the same line: a one-in-twelve ramp has ratio 1/12, percent grade about 8.333, and an angle of about 4.76 degrees.
A six-percent highway grade is a rise of six over a run of one hundred, ratio 0.06, and an angle of about 3.43 degrees. The calculator uses the arctangent of rise over run, so a negative rise (a downhill) yields a negative percent, a negative ratio, and a negative angle, while a zero rise is a level grade of zero.
The run is the horizontal projection, never the hypotenuse; mixing those two is the classic error that understates a ramp's steepness because the tape along the slab is longer than the plan distance. Units cancel, so metres over metres, inches over inches, and feet over feet all produce the same percent, ratio, and angle.
Where an elevation grade calculator earns its keep
Wheelchair-ramp shops live on the one-in-twelve rule: a rise of one over a run of twelve is the ADA maximum for an unassisted ramp in many jurisdictions, about 8.33 percent and just under five degrees. Typing those two lengths here confirms the percent, the decimal ratio, and the angle before a carpenter cuts stringers or a metal shop rolls a ramp.
Civil and highway designers post percent grade on profiles: a six-percent climb over a hundred-metre run is six metres of elevation, and the angle tells the paving crew how the paver sits. Driveway and site-drainage contractors need a minimum grade so water leaves a slab, and a maximum so cars do not scrape or lose traction; sending rise and run returns all three representations in one shot.
Landscape architects set walks, swales, and retaining-wall backfill to a target percent; surveyors convert a rod reading (rise) and a tape (run) into a grade they can stamp on a cut sheet. Curriculum authors and LMS auto-graders pin goldens: rise 1 and run 12 must stay 8.333... percent.
The tool is elevation grade from rise and horizontal run, not a two-point line slope, not a converter among already-known percent, degree, and ratio formats, and not an angle of elevation from an observer to a distant object; those are different search intents. It also does not size landings, rest intervals, or drainage inlets.
What you can do with it
Wheelchair ramps and ADA 1:12 checks
Send rise 1 and run 12 to confirm the percent grade, decimal ratio, and angle before cutting stringers or rolling a metal ramp.
Road and driveway profile grades
A posted six-percent climb is rise 6 over run 100; the calculator returns percent, ratio, and degrees for the profile stamp.
Site drainage and landscape slopes
Convert a rod reading and a tape distance into percent grade so walks, swales, and slabs shed water without exceeding a traction limit.
FAQ
How is elevation grade calculated from rise and run?
Percent grade is 100 × rise / run, the ratio is rise / run, and the angle in degrees is atan(rise/run) × 180/π. Send finite rise and a non-zero run in the same linear unit.
What happens if the run is zero?
Elevation grade is undefined when the horizontal run is zero, because percent, ratio, and angle would require division by zero. Failed tasks are not billed.
Can rise be negative for a downhill?
A zero rise is a level grade of zero.
What units should I use for rise and run?
Any shared linear unit: metres, millimetres, inches, or feet. Units cancel, so the percent, ratio, and angle are the same as long as rise and run use the same unit. Do not mix a hypotenuse tape with a horizontal run.
Should I measure the run along the slope or horizontally?
Horizontally. The run is the plan distance between the two points, not the length of the sloped surface. A tape laid along the slab reads longer, which makes a ramp look gentler than it really is.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/build/elevation-grade \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"rise":1,"run":12}'const res = await fetch("https://api.kit.forhosting.com/build/elevation-grade", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"rise": 1,
"run": 12
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/build/elevation-grade",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"rise": 1,
"run": 12
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/build/elevation-grade", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"rise":1,"run":12}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"rise":1,"run":12}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/build/elevation-grade", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"rise": 1,
"run": 12
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "build.elevation_grade",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
A zero run makes the grade undefined and the task fails with invalid_input; missing or non-finite values fail the same way.
How percent grade, ratio and angle follow from rise and run
The formula field restates percent_grade = 100 × rise / run, ratio = rise / run, and angle_deg = atan(rise/run) × 180/π so a drawing note can quote the identity next to the numbers.
What you send, which units to use, and how validation fails
Send two required finite numbers named rise and run. A downhill of rise −4 over run 50 yields a negative percent and direction downhill. Missing fields, empty strings, NaN, and Infinity fail the same way, naming the field so a form can highlight that control. Failed tasks are not billed. The same input always produces the same rounded output, which is the contract estimating sheets, CNC ramps, and edge workers rely on when they pin a one-in-twelve as 8.333 percent. Rise is the signed vertical change from the start station to the end station; aliases height, vertical, elevation, delta_h, and dy are accepted. Run is the signed horizontal distance between those stations; aliases horizontal, distance, length, dx, and horizontal_run are accepted. JSON numbers and numeric strings both work. On success the response echoes the cleaned rise and run, publishes percent_grade as one hundred times rise over run, ratio as rise over run, angle_deg as the arctangent in degrees, direction as uphill, downhill, or level from the sign of the ratio, and formula as the identity that produced them. A worked ADA case: rise 1 and run 12 yields percent_grade 8.333..., ratio 0.0833..., and angle_deg about 4.764 degrees, direction uphill. A six-percent road: rise 6 and run 100 yields percent_grade 6, ratio 0.06, and angle_deg about 3.434 degrees. Successful API calls use the published base of $0.002 per item.
Technical questions
What does the elevation grade calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.