# Slope (Gradient) of a Straight Line

The Slope (also called Gradient) of a straight line shows how steep a straight line is.

## Calculate

The method to calculate the slope is:

Divide the change in height by the change in horizontal distance
Slope  =
 Change in Y Change in X

## Examples:

The slope of this line =
 3 3
=  1

So the slope is equal to 1

slope =
 4 2
=  2

(The line is steeper, and so the slope is larger)

slope =
 3 5
=  0.6

(The line is less steep, and so the slope is smaller)

## Positive or Negative?

Important:

• Starting from the left end of the line going across to the right is positive
(but going across to the left is negative).
• Up is positive, and down is negative

slope =
 -4 2
= –2

(That line goes down as you move along, so it has a negative slope.)

## Straight Across

slope =
 0 5
=  0

(A line that goes straight across has a slope of zero.)

## Straight Up and Down

slope =
 3 0
= undefined

That last one is a bit tricky ... you can't divide by zero,
so a "straight up and down" line's slope is "undefined".

## Rise and Run

Sometimes the horizontal change is called "run", and the vertical change is called "rise" or "fall":

They are just different words, none of the calculations change