FreeToolStation

Slope Calculator

Slope as a ratio, a percentage and an angle, with the line equation.

Geometry Calculators Free, no sign-up Runs in your browser
—
Slope
—
As a percentage
—
As an angle
—
Line equation
—
Perpendicular slope
MeasureValue
A gradient written as 1 in 10 means one unit of rise for ten of run, which is 10%, not 1%. Road and ramp signs use the percentage; drawings often use the ratio.

About the Slope Calculator

Slope Calculator gives the gradient between two points in every form it gets quoted in: as a ratio, as a percentage, as an angle in degrees, and as a 1-in-n figure. Those four describe the same thing and are constantly confused, which is the main reason for showing them together.

The percentage and the ratio are the pair that cause most trouble. A gradient of 1 in 10 means one unit of rise for every ten of run, which is a 10 per cent slope, not 1 per cent. Road signs use the percentage; engineering drawings often use the ratio; a wheelchair ramp standard of 1 in 12 is about 8.3 per cent.

A vertical line is reported as undefined rather than infinite, with the rise given. Dividing by a zero run has no value, and saying so is more useful than returning a number that would then be used in further arithmetic.

The page shows its working, not just its answer. Where there is a formula it is printed with your own numbers substituted in, so you can check the result rather than take it on trust -- which is the difference between a calculator you can use for something that matters and one you cannot.

Everything runs inside your browser. What you type is never uploaded, never logged and never stored, and the calculator keeps working if your connection drops after the page has loaded.

How to use the Slope Calculator

  1. Enter x1, y1 and x2Decimals are fine, and thousands separators are accepted and ignored.
  2. Read the slope, as a percentage and as an angleThe figures update as you type. The Calculate button is there if you would rather press something, but nothing waits for it.
  3. Copy or check the resultCopy the summary with the copy button, or open the table to check it row by row and read the formula with your own numbers in it.

Features

  • Shows slope, as a percentage, as an angle, line equation and perpendicular slope together, so you are not running it twice
  • A results table you can read across
  • Prints the formula with your own figures substituted in
  • Updates as you type, with no button to press and no page reload
  • Copy the result in one click
  • Free, no sign-up, and it runs entirely in your browser

Who uses this tool

The slope calculator is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:

  • Working out a ramp or driveway gradient
  • Converting a slope between percentage and angle
  • Finding the equation of a line through two points
  • Getting the perpendicular slope for a normal line

Frequently asked questions

Is 1 in 10 the same as 10%?

Yes. One unit of rise per ten of run is a tenth, which is 10 per cent. It is not 1 per cent, which is the usual misreading.

How do I convert slope to an angle?

Take the arctangent of the slope. A slope of 1 is 45 degrees; a slope of 0.1 is about 5.7 degrees.

What is a perpendicular slope?

The negative reciprocal. A line at right angles to a slope of 2 has a slope of -0.5.

If the slope calculator is not quite what you need, these other free tools solve closely related problems, and there are 16 more in geometry calculators.

Midpoint Calculator

Midpoint, missing endpoint and any division ratio.

Geometry Calculators Use tool

Checked and rebuilt on 2026-10-14. The method this calculator uses is described in the section above, and corrections go through the contact page.