Scale Factor
(KS3, Year 7)

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.

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

What Is an Enlargement?

An enlargement resizes a shape. An enlargement makes a shape larger or smaller. An enlargement is a type of transformation.

Scaling Lengths, Areas and Volumes

If a scale factor is k:

• Each length on the image will be k times the length of the object.
• The area of the image will be k² times the area of the object.
• The volume of the image will be k³ times the volume of the object.

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