# What Is a Scale Factor?

## What Is a Scale Factor?

A scale factor is used to describe an enlargement.

A scale factor describes how much larger (or smaller) the enlarged shape is compared to the original shape.

### Dictionary Definition

The Oxford English Dictionary defines a scale factor as "a numerical factor by which each of a set of quantities is multiplied."

## Understanding a Scale Factor

When a shape is enlarged, the length of each side becomes larger (or smaller). Each side becomes larger (or smaller) by same amount.

The length of each side is multiplied by a scale factor.

## A Real Example of a Scale Factor

A scale factor is easier to understand with an example.

The image below shows a light blue shape being enlarged to a dark blue shape.

The scale factor is **2**. Each side of the dark blue shape is **2 ×** longer than the corresponding side of the light blue shape.

## Types of Scale Factors

Scale factors have different effects depending on how large the number is.

Scale Factor | Description | |
---|---|---|

Greater than 1 | The shape gets larger | |

Equal to 1 | The shape stays the same size | |

Greater than 0, less than 1 | The shape gets smaller | |

Negative | The shape is on the other side of the center of enlargement, and is the other way around |