Ratio Calculator

Free ratio calculator: find the ratio between two numbers and simplify it to its lowest terms. Enter two values and get the ratio instantly.

AI-ready Use this tool with AI

This tool has a free JSON API. Copy a prompt or skill below to use it with ChatGPT, Claude, or any AI agent — no API key needed.

API docs
Enter two values.

How ratio calculator works

A ratio compares two quantities by showing how many times the first contains the second. For example, a ratio of 10 to 4 means the first quantity is 2.5 times the second. Ratios can be written as fractions (10/4), with a colon (10:4), or as decimals (2.5).

This calculator computes the decimal ratio and also simplifies the ratio to its lowest terms by dividing both numbers by their greatest common divisor (GCD). For example, 10:4 simplifies to 5:2 because the GCD of 10 and 4 is 2.

Ratios are used everywhere: in recipes (2 cups flour to 1 cup sugar), in finance (price-to-earnings ratios), in maps (scale ratios), and in probability. The simplified form makes ratios easier to compare and understand.

Frequently asked questions

How do I calculate a ratio?
Divide the first number by the second. For example, the ratio of 10 to 4 is 10/4 = 2.5. The calculator also shows the simplified integer ratio (5:2).
How do I simplify a ratio?
Find the greatest common divisor (GCD) of both numbers, then divide both by it. For 10:4, the GCD is 2, so the simplified ratio is 5:2.
What is a ratio used for?
Ratios compare quantities: recipe proportions, financial metrics, map scales, odds, and more. They tell you the relative size of one quantity to another.
Can ratios have decimals?
Yes. The decimal ratio (like 2.5) is often useful for calculations. The simplified integer ratio (like 5:2) is easier to communicate and compare.