Slope Calculator: Slope, Angle and Equation of a Line
Enter two points on the line. You get the slope (gradient), the angle it makes with the x-axis, the intercepts and the line's equation.
- Nothing you type is stored
- Free
- No signup
Slope (m)
1.5
- Equation
- y = 1.5x + 0.5
- Angle with x-axis
- 56.3099 °
- y-intercept (c)
- 0.5
- x-intercept
- −0.3333
As a fraction m = 3/2; general form: 3x − 2y + 1 = 0.
Show working
- m = (y₂ − y₁) / (x₂ − x₁)
- m = (8 − 2) / (5 − 1) = 6 / 4 = 1.5
- c = y₁ − m·x₁ = 2 − 1.5 × 1 = 0.5
- y = 1.5x + 0.5
- θ = tan⁻¹(m) = 56.3099°
How to use
- Enter the first point (x₁, y₁).
- Enter the second point (x₂, y₂).
- Read the slope, angle and equation.
Good to know
Slope m = (y₂ − y₁) / (x₂ − x₁), the rise over the run. Its angle with the positive x-axis is θ = tan⁻¹(m), from NCERT Class 11 "Straight Lines". A positive slope rises to the right, a negative one falls.
The line's equation in slope-intercept form is y = mx + c, where c = y₁ − m·x₁ is where the line crosses the y-axis. With whole-number points the calculator also gives the slope as a fraction and the general form ax + by + c = 0.
If x₁ = x₂ the line is vertical: its slope is undefined and its equation is x = constant. A horizontal line has slope 0. Parallel lines have equal slopes; perpendicular lines have slopes that multiply to −1.
Questions
What is the slope formula?
m = (y₂ − y₁) ÷ (x₂ − x₁).
What is the slope of a vertical line?
Undefined, because x₂ − x₁ = 0. Its equation is x = a constant.
How do I find the angle of a line?
θ = tan⁻¹(m). A slope of 1 means 45°.
How do I tell if two lines are perpendicular?
Multiply their slopes. If the product is −1 (and neither line is vertical), they are perpendicular.
Is anything I enter stored?
No. The calculation runs in your browser and nothing is sent to a server.