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Slope Calculator: Slope, Angle and Line Equation

Enter two points on a line to get its slope, its angle in degrees and its equation.

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Formula

  • m = (y2 - y1) / (x2 - x1)
  • b = y1 - m × x1, line: y = mx + b
  • angle = atan(m) in degrees

Worked example

Points (1, 2) and (3, 6): m = (6 - 2) / (3 - 1) = 2, b = 2 - 2 × 1 = 0, so the line is y = 2x and the angle is atan(2) = 63.4349 degrees.

Frequently asked questions

How do I find the slope between two points?

Divide the change in y by the change in x: m = (y2 - y1) ÷ (x2 - x1). For (1, 2) and (3, 6) that is 4 ÷ 2 = 2.

How do I get the equation of the line?

Use y = mx + b, then b = y1 - m × x1. For (1, 2) with m = 2, b = 2 - 2 = 0, so the line is y = 2x.

What if the line is vertical?

If both x values are equal, the change in x is zero and the slope is undefined, so the calculator reports a divide by zero. The line is simply x = that value.

How is the angle calculated?

The angle with the x axis is the arctangent of the slope. A slope of 2 gives atan(2) = 63.4349 degrees; a negative slope gives a negative angle.

How we calculate

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