Rule of Three

Easily calculate direct and inverse proportions

Frequently asked questions

What is direct and inverse proportion?▼

Direct: when A increases, B increases in the same proportion (e.g. price and quantity). Inverse: when A increases, B decreases (e.g. speed and time).

Can I use decimal numbers?▼

Yes. The tool accepts decimal numbers in any field. The result is calculated with appropriate precision.

Calculate discounts in multiple ways: percentage, fixed amount, final price or original price

Convert between percentage and decimal in real time (e.g. 50% ↔ 0.5)

Calculate percentages in multiple ways: X% of Y, X is what % of Y, percent change and more

Basic calculator with addition, subtraction, multiplication and division

Convert Arabic numbers to Roman numerals (1 to 3999)

Convert LaTeX formulas to SVG or PNG images for use in documents and presentations