Proportion Calculator

Use our free proportion calculator to solve for the missing term in a proportion. Enter three known values and find the fourth using cross-multiplication.

Math

Find

Formula

A proportion states that two ratios are equal, written as a:b = c:d. Solve for any missing term using cross-multiplication: a×d = b×c.

A/B = C/D → A×D = B×C

Percentage: The percentage value you want to apply

Number: The original number or value

Result: The calculated result

How It Works

1Select which term (A, B, C, or D) is missing.
2Enter the three known values.
3Click Calculate to solve for the missing term.
4The result shows the value using cross-multiplication.

Examples

Solve 2:3 = 10:x

1.Select D (fourth term) as missing.
2.Enter A=2, B=3, C=10.
3.Cross-multiply: 2 × D = 3 × 10
4.D = (3 × 10) ÷ 2 = 15.

Result: 15

Frequently Asked Questions

Cross-multiplication solves proportions by multiplying the extremes and means: a × d = b × c. If one term is unknown, divide the product of the known cross by the remaining known term.

The calculator will still work and return the value of the term you selected as 'missing.' You can use this to verify if four numbers form a true proportion.

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CalculateMe Team

Last updated: 2026-07-13

Proportion Calculator

Formula

How It Works

Examples

Solve 2:3 = 10:x

Frequently Asked Questions

What is cross-multiplication?

What if I enter all four values?

Related Calculators

Proportion Calculator

Formula

How It Works

Examples

Solve 2:3 = 10:x

Frequently Asked Questions

What is cross-multiplication?

What if I enter all four values?

Related Calculators