Local and instant calculation

Rule of Three Calculator

Solve proportions, prices, percentages, quantities and conversions with a simple rule of three.

Enter the three known values and the tool will automatically calculate the fourth proportional value.

Free finance tool

Rule of Three Calculator

Calculate simple rule of three operations for proportions, prices, quantities and conversions.

Rule of three

Calculate proportions quickly

If A corresponds to B, calculate what corresponds to C.

Result X

250.00

Formula

X = B × C / A

1

How to calculate a simple rule of three

Enter the three known values in the corresponding order. The tool applies the proportion and automatically calculates the fourth value. This method is useful when two quantities have a direct proportional relationship.

2

What you can use the rule of three for

  • Calculate prices for a specific quantity.
  • Find equivalent quantities for recipes or mixtures.
  • Compare compatible measurements and units.
  • Calculate consumption, performance or production.
  • Solve proportions for estimates.
  • Calculate equivalent values for purchases and sales.
3

Tips to avoid mistakes

  • Place related values in the same position.
  • Use compatible units before calculating.
  • Convert grams, kilograms, meters or other units when necessary.
  • Do not enter zero in a position used as a divisor.
  • Review the result before using it in an estimate.

Check the units before calculating

Related values should use compatible units. For example, avoid mixing kilograms and grams unless you convert them to the same unit first.

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