Rule of Three Calculator
Enter three values and the fourth is calculated proportionally - right in your browser.
💡 What's this for?
With this tool you work out the classic rule of three: you know three related values and want to find the fourth. Handy in everyday life, for example to quickly scale prices, quantities or recipe ingredients.
Enter three values and leave one field empty. The empty field will be calculated proportionally (A is to B as C is to D).
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Leave exactly one field empty.
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