Free tool
Scale factor calculator
Enter the original size and the new size. The scale factor, the ratio and the percent change update as you type.
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How it works
How it works
The scale factor is new size divided by original size. Above 1 is an enlargement and below 1 is a reduction. Areas change by the scale factor squared, so doubling every length makes the area four times larger.
Example: a 4-inch photo enlarged to 10 inches has a scale factor of 10 / 4 = 2.5, a 150% increase, and its area grows 6.25 times. A 6-inch side on the same photo becomes 6 x 2.5 = 15 inches.
FAQ
About this calculator
How do I find a scale factor?
Divide the new length by the original length. 10 divided by 4 is a scale factor of 2.5.
What does a scale factor of 0.5 mean?
Every length is half its original size, and the area is one quarter.
How is a map scale written?
As a ratio such as 1 : 24,000, meaning one unit on the map is 24,000 of the same units on the ground.
Is anything saved?
No. The math runs in your browser and nothing you enter is sent to us.
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General information, not tax or legal advice. How we write and check our tools.