For the 1:x ratio, enter and receive just the number x (for example, for "1:10" enter 10). The ratio shows how many horizontal length units correspond to one vertical rise unit.
Result
This page has no server side at all. The table you paste is parsed by JavaScript inside your own browser, the chart is drawn on a canvas element on your machine, and the export file is assembled locally. Nothing is uploaded, stored or written to any log. You can disconnect from the network after the page has loaded and everything will still work — which is the simplest way to verify the claim yourself.
Facts and limits of this method
| Percent → degrees formula | angle = arctan(percent / 100) |
|---|---|
| Degrees → percent formula | percent = tan(angle) × 100 |
| 45° slope | = 100% = ratio 1:1 |
| Degree range | 0° (flat) to nearly 90° (vertical) — excluding true vertical |
When it misleads you
- Slope percent and slope degrees are related nonlinearly through the tangent function — a 100% slope corresponds not to 90° but to exactly 45°; for slopes steeper than 100%, percent grows much faster than degrees.
- The 1:x ratio is conventionally written so the first number (usually 1) is the vertical rise and x is the horizontal run; the larger x is, the gentler the slope. The converter works with the number x itself, not the full "1:x" notation.
- As slope approaches vertical (90°), the percent grade approaches infinity while x in the 1:x ratio approaches zero — the converter won't produce a result for a perfectly vertical slope.
- Rounding is applied only to the displayed result — internal calculations use the full precision of JavaScript floating-point numbers.
How it is calculated
The entered value is first converted to degrees: percent via arctangent (angle = arctan(value/100)), a 1:x ratio also via arctangent (angle = arctan(1/x)).
If the "from" unit is already degrees, this step leaves the number unchanged.
The angle in degrees is then converted to the target unit using the inverse formula — to percent via tangent, to a 1:x ratio via cotangent (1/tan(angle)).
The result is rounded to the chosen number of decimal places and updates instantly whenever the value, units or precision change.
Questions and answers
What does a 100 percent slope mean?
100% means rising one meter (or any unit) vertically for every meter of horizontal distance — this corresponds to an angle of exactly 45°, not 90° as sometimes mistakenly assumed.
How do I read a "1:10 slope"?
It means 10 units of horizontal distance for every 1 unit of vertical rise — a fairly gentle slope, equivalent to 10% or about 5.7°.
Why does percent grow much faster than degrees on very steep slopes?
Because the relationship between them is the tangent of the angle, not a linear function: as the angle approaches 90°, the tangent — and so the slope percent — approaches infinity.
Is my data sent anywhere?
No, the whole calculation runs in your browser.