AnkhKit

Rule of Three Calculator (Direct Proportion)

Runs 100% in your browser — your files never leave your device.

The rule of three solves the everyday proportion: if A corresponds to B, what does X correspond to? Prices, recipes, fuel consumption, unit conversions — anywhere two quantities grow together. Type the three values you know and the fourth appears instantly, with the proportion spelled out above the answer.

How it works

  1. 1

    Enter the known pair

    Value A and the value B that corresponds to it — for example, 3 items and $6.

  2. 2

    Enter the third value

    The amount you want to find the counterpart for — for example, 5 items.

  3. 3

    Read the fourth value

    The answer appears live, with the full proportion restated so you can sanity-check it.

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