## Purpose

## Return value

## Arguments

*known_ys*- An array or range of numeric data points (dependent values).*known_xs*- An array or range of numeric data points (independent values).

## Syntax

## Usage notes

The SLOPE function returns the slope of a regression line based on known y values and known x values. A regression line is a "best fit" line based on known data points.

The slope of a line is a measure of steepness. Mathematically, slope is calculated as "rise over run", or change in y over the change in x. For example, if a line has a slope of 2/1 (2), then if y increases by 2 units, x increases by 1 unit.

### Example

In the example shown, the formula in E5 is:

```
=SLOPE(B5:B9,C5:C9) // returns -2
```

This formula returns -2, based on *known_ys* in C5:C9, and *known_xs* in B5:B9.

### Equation

In statistics, a best fit line does not normally lie exactly on the known x and y points. The equation used by the SLOPE function in Excel is based on the mean of known x's and y's:

For the example shown, this formula can be manually recreated like this:

```
=SUM((B5:B9-AVERAGE(B5:B9))*(C5:C9-AVERAGE(C5:C9)))/SUM((B5:B9-AVERAGE(B5:B9))^2)
```

The calculated result from the SLOPE function and the manual formula are the same.

### Notes

- If there is only one set of points, SLOPE will return #DIV/0!
- If the count of
*known_ys*is different from*known_xs*, SLOPE returns #N/A