CalculatorX

Reference

Proportion Calculator

Proportion Calculator keeps a ratio A:B and scales it. If A is 2, B is 3, and the known value of A is 20, B becomes 30. Slope questions that are “rise for this run” can use the same scaling if you set the parts yourself.

Proportion Calculator keeps a ratio A:B and scales it. If A is 2, B is 3, and the known value of A is 20, B becomes 30. Slope questions that are “rise for this run” can use the same scaling if you set the parts yourself.

Reviewed 2026-11-08. The result is an educational estimate, not professional advice.

Enter your values

This calculation stays in your browser. Nothing is sent when you press Calculate.

Result

Enter values to calculate.

Formula

B = value of A ÷ A × B.

Example

Ratio 2:3 and a value of 20 for A gives 30 for B.

Illustration for the Ratio Calculator used by CalculatorX.
Illustration only. Use the formula and the result box for the number.

How to use Proportion Calculator

Enter both parts of the ratio and the value you already know for A. The page returns B.

The formula that actually runs is: B = value of A ÷ A × B.

Ratio 2:3 and a value of 20 for A gives 30 for B.

Where this estimate stops

A zero in part A cannot be scaled. Ratios do not become percentages until you divide one part by the total.

The calculation stays in your browser. CalculatorX does not save the numbers as an account.

If you need a different figure, look at Ratio Calculator, Ratio Calculator, Slope Calculator, Golden Ratio Face Calculator.

How to use this calculator

  1. Start with the numbers you already have. Enter both parts of the ratio and the value you already know for A. The page returns B.
  2. Press Calculate. The result uses only the fields on this form and the formula printed under it.
  3. Read the limit. A zero in part A cannot be scaled. Ratios do not become percentages until you divide one part by the total.

Questions about Proportion Calculator

How does Proportion Calculator get its result?

Enter both parts of the ratio and the value you already know for A. The page returns B.

What formula is on the proportion calculator page?

B = value of A ÷ A × B.

Can I trust “proportion calculator” as a final decision?

A zero in part A cannot be scaled. Ratios do not become percentages until you divide one part by the total.

Is this stored or sent anywhere?

No. The page calculates in your browser and does not create an account.

What this helps you do

  • Estimate Proportion from the inputs you already have.
  • Check the result against the formula and the worked example.
  • Change one value at a time and compare the new estimate.

Limits to keep in mind

  • The figure is only as complete as the inputs on this form.
  • Rounding, fees, and local rules can change the real-world number.
  • Use it to learn and compare. Confirm important finance or health decisions with a qualified professional.