Mathematics
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Mathematics
Rule of three calculator
Find the fourth value in a proportion.
Your result
Complete the fields and calculate.
Example
Rule of three calculator
3 items cost 12. 5 items cost 20.
FAQ
Frequently asked questions
How accurate is the result?+
The calculator uses the stated formula and only rounds the display. Accuracy depends on your inputs.
Is this calculator really free?+
Yes. Use it as often as you like without an account or registration.
Are my entries stored?+
The calculation runs directly in your browser. Calculator values are stored locally only when you explicitly add a result to “My results”. Favourites and history also remain locally on your device.