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Ratio and proportion calculator

Scale quantities and compare proportions. Simple, private, right in your browser.

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A LITTLE GUIDANCE

How to use this tool

  1. Choose ratio simplification or missing-value proportion.
  2. Enter the labelled values.
  3. Calculate the reduced ratio or the missing denominator x.

A worked example

Simplify 12:18 → 2:3; solve 2/3 = x/12 → x = 8.

What to know

Simplification accepts nonnegative integers and uses the greatest common divisor. Both ratio sides cannot be zero. Proportion mode solves A/B = C/x and rejects zero denominators.

Supported inputs and limits

Ratio integers up to 10¹²; other values within ±10¹⁵.

Where is my data processed?

In your browser. Cloud saving is optional: only the supported inputs, settings or files you explicitly choose are uploaded. Download or save anything you want to keep before closing the page. Read our privacy details.

Further reading

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