CalculateMeasure

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Proportion Calculator

Solve a direct proportion of the form A/B = C/X for the unknown value X.

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Calculator guide

How to use the Proportion Calculator

Solve a direct proportion of the form A/B = C/X for the unknown value X. Enter the requested values and select Calculate. The result and supporting values are produced locally in your browser.

Formula

X = B × C ÷ A

Worked example

For 2/5 = 8/X, X = 5 × 8 ÷ 2 = 20.

What to keep in mind

  • This tool solves a direct proportion with X in the fourth position.
  • Keep units consistent across corresponding terms.

Methodology

This calculator uses deterministic arithmetic and performs the calculation locally in your browser. Verify assumptions, units, and source values for your specific use case.

Review standard: Level A · Standard formula. How calculator reviews work.

Frequently asked questions

What does this calculator calculate?

Solve a direct proportion of the form A/B = C/X for the unknown value X.

How is the result calculated?

X = B × C ÷ A.

Can I use the result for an important decision?

Use the result as a calculation aid and verify the inputs, assumptions, and applicable professional or regulatory requirements before relying on it for an important decision.

Does CalculateMeasure store the values I enter?

The calculator performs its arithmetic in your browser. The calculator itself does not need to send your entered values to a server to produce the result.