🧮
Rule of Three Calculator
This calculator solves direct proportions using the classic rule of three. Enter A, B and C to find X in the proportion A:B = C:X. Useful for pricing, quantities, recipes, discounts and everyday calculations.
Frequently Asked Questions
The rule of three is a method to solve a proportional relationship when three values are known and the fourth is unknown.
How this calculator works
Formula explanation
**Formula:** X = (B × C) / A
Worked example
**Example:** If 2 kg cost 6, then 5 kg cost X = (6 × 5) / 2 = 15.
Explore more tools in this category
See all calculators in Mathematics.
Continue with related calculators
If you need a nearby calculation or want to compare a related result, these pages are the next best places to continue.
Related Calculators
Discover similar tools to continue your calculation or compare related results.