Proportion Calculator with Steps

Enter three values and leave the missing value blank. Choose direct or inverse proportion to see the answer and each calculation step.

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How do the quantities change?

Direct proportionMore → moreMore weight → higher priceInverse proportionMore → lessMore workers → less time

Not sure?

Direct: double one quantity and the other doubles too, at a fixed rate. Inverse: double one and the other halves, with a fixed total. Choose the model that fits your situation; three numbers alone cannot decide it. These direction cues describe positive quantities.

Enter three values

Leave the value you want to find empty. The result updates automatically.

Try an example

Quantity 1

Quantity 2

First situation

First situation: Quantity 1

First situation: Quantity 2

Second situation

Second situation: Quantity 1

Second situation: Quantity 2

Numbers like 12, 12.5, 12,5 or 3/4. No thousands separators. Use the same unit in each column.

Add labels & units

Quantity 1Label (optional)Unit (optional)

Quantity 2Label (optional)Unit (optional)

Labels describe your numbers; they do not convert units.

More options

Maximum decimal placesExtra zeros are hidden. Exact fractions stay available.Decimal separatorFor ambiguous entries such as 1.234. Grouping separators are never supported.

Full keyboard for fractions and minus signs

Up to 18 whole-number digits and 12 decimal places, or integer fractions with up to 18 digits per part. No exponent notation. Signed values follow the equations but must make sense for your situation.

How to use the proportion calculator

Choose direct or inverse proportion, or start with an example above.
Enter three values and leave the missing value blank. Keep the same unit within each column.
Read the answer, follow the steps and use the verification to check the calculation.

Direct or inverse proportion?

Direct proportion

More → more · Less → less

For positive quantities, twice the quantity means twice the result. The ratio stays constant, as with price and quantity at a fixed unit price.

Inverse proportion

More → less · Less → more

For positive quantities, twice the quantity means half the result. The product stays constant, as with workers and time for the same job at equal productivity.

How cross multiplication works

For a direct proportion, equal ratios have equal cross products. If 750 g cost EUR 6, the price x for 1,200 g is:

750 / 6 = 1200 / x → 750 × x = 6 × 1200 → x = 9.6

Check: 750 × 9.6 = 6 × 1200 = 7200. For an inverse proportion, keep each row’s product equal instead: 4 × 6 = 8 × x, so x = 3 hours.

Everyday proportion examples

Price · direct: 750 g cost EUR 6 → 1,200 g cost EUR 9.60.
Recipe · direct: 4 portions need 300 g → 6 portions need 450 g.
Workers · inverse: 4 workers need 6 hours → 8 need 3 hours, at equal productivity.
Map scale · direct: 3 cm represent 1.5 km → 8 cm represent 4 km.

Frequently asked questions

Can I solve for any of the four values?

Yes. Leave exactly one field blank and enter the other three. The calculator rearranges the chosen relationship to solve that position.

Can I enter fractions and decimal numbers?

Yes: use a fraction such as 1/3 or a decimal such as 2.5 or 2,5. Avoid thousands separators. If a value such as 1,234 is ambiguous, explicitly select its decimal format or remove the separator when you mean 1234. An ≈ sign marks a rounded decimal; the fraction remains exact.

Does the calculator convert units?

No. Use one unit per column: convert kilograms to grams before combining them. Labels and units describe your quantities. The calculator cannot decide whether a direct or inverse model fits the real situation.

Why does a zero value sometimes prevent a result?

A zero divisor cannot produce a unique answer. Inverse proportions require nonzero values. A negative number may work mathematically, but check whether it makes sense for quantities such as workers or time.