Ratio Calculator
Simplify ratios to their lowest terms or solve for the missing value in a proportion.
Simplify the ratio A : B
How ratios and proportions work
A ratio compares two quantities of the same kind. The ratio 3:4 means for every 3 of one thing, there are 4 of another. To simplify, divide both parts by their GCD — so 12:16 simplifies to 3:4.
A proportion states that two ratios are equal: A:B = C:D. To find a missing value, cross-multiply: D = (B × C) / A. This is the foundation of recipe scaling, map reading, unit conversion, and similar triangle problems.
Real-world uses of ratios
Recipe scaling
Double or halve any recipe by keeping the ingredient ratios the same.
Map scales
A 1:50,000 map means 1 cm on the map = 50,000 cm (500 m) in reality.
Financial ratios
Price-to-earnings (P/E) ratio compares stock price to earnings per share.
Mixing solutions
A 1:3 bleach-to-water solution means 1 part bleach for every 3 parts water.
Screen aspect ratios
16:9 widescreen means 16 units wide for every 9 units tall.
Gear ratios
A 3:1 gear ratio means the output shaft turns once for every 3 input turns.
Frequently Asked Questions
A ratio is a comparison of two quantities. For example, 4:2 means for every 4 of one thing, there are 2 of another. Simplified by their GCF (2), this becomes 2:1.