Ratio and proportion calculator

Solve a missing value in an equivalent ratio and see the scale factor behind the proportion.

01 · Your editable starting point

Your editable starting point

Change the values you know. Every result updates instantly in your browser.

03 · What the numbers mean

Solve a missing value in an equivalent ratio and see the scale factor behind the proportion.

Your resultWhat the numbers meanYour result

3 : 4 = 21 : xThe missing fourth value that keeps both ratios equal.28

Scale factorHow many times the first ratio was enlarged or reduced.7

First ratioThe first number divided by the second.0.75

04 · Guidance and limitations

Solve a missing value in an equivalent ratio and see the scale factor behind the proportion.

ⓘ This is an educational estimate, not a diagnosis or a personal medical recommendation.

Do I need to press Calculate?

No. Every result updates immediately when an input changes.

Are the entered numbers submitted?

No. The calculation runs in your browser without registration.

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