PDF Editors PDF Converters PDF Utilities Calculators Geometry & Trig Math Tools Color Modifiers Color Generators Color Schemes Colors Tutorial Image Colors Text Tools List Tools Text Analyzers Numbers Date & Time Image Editors Image Adjustments Image Effects Image Generators Image Converters Image Utilities Randomness Files Code Formatters Dev Converters Dev Utilities Videos Finance Prize Bond Blog

Browse Categories

PDF Editors PDF Converters PDF Utilities Calculators Geometry & Trig Math Tools Color Modifiers Color Generators Color Schemes Colors Tutorial Image Colors Text Tools List Tools Text Analyzers Numbers Date & Time Image Editors Image Adjustments Image Effects Image Generators Image Converters Image Utilities Randomness Files Code Formatters Dev Converters Dev Utilities Videos Finance Prize Bond Blog

Math Tools

Rule of Three Standard Deviation GCD LCM Fibonacci Numbers Proportions Prime Number Checker Roman Numeral Converter

Home›Math Tools›Rule of Three

Rule of Three

Proportional calculation: if A relates to B, then C relates to X.

Input

A

B

C

Options

Proportion type

Direct Inverse

Decimal places

Related Tools

Keep Working With Similar Tools

Browse Math Tools

📊Standard Deviation

Statistical standard deviation

Greatest common divisor

Least common multiple

🌀Fibonacci Numbers

Generate Fibonacci sequence

(c) 2026 ToolAero - 150+ free online tools. | Contact Us