Enter two points and find the slope between them, along with the full equation of the line in slope-intercept form.
Slope Calculator
LiveSlope (m)
2
Y-intercept (b)
-1
Equation
y = 2x - 1
A vertical line (same x1 and x2) has an undefined slope.
The formulas
Slope: m = (y2 - y1) / (x2 - x1)
Y-intercept: b = y1 - m x x1
Equation: y = mx + b
Example
Points (2, 3) and (8, 15): m = (15-3)/(8-2) = 12/6 = 2. b = 3 - 2x2 = -1. Equation: y = 2x - 1.
Step-by-step guide
- Enter the coordinates of two points on the line.
- Read the slope - a measure of steepness (rise over run).
- Read the y-intercept and full equation in y = mx + b form.
Common mistakes
Swapping the order in the numerator and denominator - it must be (y2-y1) over (x2-x1), consistently, not mixed.
Forgetting that a vertical line has an undefined slope (division by zero), not a slope of zero - a slope of zero is a horizontal line instead.
Frequently asked questions
What does a negative slope mean?
A negative slope means the line goes downward as you move left to right. A positive slope goes upward, and a slope of zero is perfectly flat (horizontal).
What is the y-intercept?
It's the y-value where the line crosses the vertical (y) axis - in other words, the value of y when x equals zero.
How is slope used outside of math class?
Slope shows up in road grade (steepness), roof pitch, wheelchair ramp regulations, and rate-of-change concepts in finance and science.
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