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Ratio Calculator: Solve A:B = C:? and Simplify Ratios

Solve a proportion like 2 : 3 = 10 : ?, simplify any ratio to its lowest terms and see it as 1 : n.

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How to use the ratio calculator

  1. Type your numbers in the boxes (pick your currency or units if asked).
  2. The answer updates as you type: no button to press.
  3. Copy the result, or share it on WhatsApp with one tap.

Questions

How do I solve A : B = C : ?

Multiply B by C and divide by A. For 2 : 3 = 10 : ?, the answer is 3 × 10 ÷ 2 = 15.

Is my data private?

Yes. Everything happens inside your own browser: nothing you type or choose is uploaded to us or anyone else.

Is it free?

Completely free, with no sign-up, no watermark and no limit on how many times you use it. Light ads keep the site running.