About this calculator
A vertical line has an undefined slope.
How to use it
- Enter the first point.
- Enter the second point.
- Read the slope and equation.
The formula
m = (y₂ − y₁) ÷ (x₂ − x₁); c = y₁ − m x₁
- m
- slope
- c
- y-intercept
Worked example
Points (1, 2) and (4, 8)
- m = (8 − 2) ÷ (4 − 1) = 2.
- c = 2 − 2 × 1 = 0, so y = 2x.
- Angle with the x-axis ≈ 63.43°.
What the result means
Parallel lines have equal slopes; perpendicular slopes multiply to −1.
Assumptions
- All lengths in the same unit.
Limitations
- Results are rounded to 10 significant figures.
Frequently asked questions
What is slope?
Rise over run: the change in y divided by the change in x.
What is the slope of a horizontal line?
0.
What is a negative slope?
The line falls from left to right.
Last reviewed on 3 October 2026. Found a mistake? Tell us.