Slope Calculator
Find the slope, y-intercept and equation of the line through two points.
Results update as you type.
About this calculator
The slope of a line measures its steepness — the rise over the run between two points. This calculator takes two points and returns the slope, the y-intercept, the equation of the line in slope-intercept form, the angle of incline, and the distance between the points, with a plot of the line.
The slope is m = (y₂ − y₁) / (x₂ − x₁), the change in y divided by the change in x. From (0, 0) to (3, 6) that is 6 ÷ 3 = 2, so the line rises two units for every one across. The y-intercept b comes from b = y₁ − m·x₁ (here 0), giving the equation y = 2x, and the angle of incline is arctan(2) ≈ 63.4°. A positive slope rises left to right, a negative slope falls, and a slope of 0 is horizontal. A vertical line has no change in x, so its slope is undefined and its equation is x = constant.
Slope shows up as grade on a road, pitch on a roof, rate of change in a graph, and the coefficient in a linear equation. It is the single number that tells you how fast one quantity changes with another.
Frequently asked questions
How do you calculate slope from two points?
Slope = (y₂ − y₁) / (x₂ − x₁), the change in y divided by the change in x. From (0,0) to (3,6) the slope is 6/3 = 2.
Why is a vertical line’s slope undefined?
A vertical line has no change in x, so the slope formula divides by zero. Its equation is x = constant instead of y = mx + b.
What is the y-intercept?
It is where the line crosses the y-axis, the b in y = mx + b, found from b = y₁ − m·x₁. For the line through (0, 0) and (3, 6) it is 0.
What is the angle of incline?
It is the angle the line makes with the horizontal, equal to the arctangent of the slope. A slope of 2 gives about 63.4°.
What does a positive or negative slope mean?
A positive slope rises from left to right, a negative slope falls, a slope of 0 is horizontal, and a vertical line has an undefined slope.
Does the calculator show the distance too?
Yes. Along with the slope it gives the straight-line distance between the two points you entered.
API — use this calculator from code
Call this calculator as a free JSON endpoint — no key required. Send the field values below as query parameters or JSON. Read the full API docs →
Endpoint
GET https://calculator.free/api/v1/slope/curl
curl "https://calculator.free/api/v1/slope/?x1=0&y1=0&x2=3&y2=6"JavaScript fetch()
const r = await fetch(
"https://calculator.free/api/v1/slope/?" + new URLSearchParams({
"x1": "0",
"y1": "0",
"x2": "3",
"y2": "6"
}));
const data = await r.json();
console.log(data.results);Results are estimates for general guidance only, not financial, medical or tax advice.