Ratio Calculator
Simplify a ratio and convert it to a decimal.
Results update as you type.
About this calculator
A ratio calculator reduces a ratio like 16:9 to its simplest whole-number form and shows it as a decimal. It divides both numbers by their greatest common divisor to simplify them, and divides the first by the second to give the decimal equivalent.
For example, 1920:1080 share a common factor of 120, so the ratio simplifies to 16:9, which as a decimal is 1920 ÷ 1080 ≈ 1.778. That is exactly why a 1920×1080 screen is described as 16:9 widescreen.
Use it for screen and image aspect ratios, scaling a recipe up or down, map and model scales, mixing paint or fuel, gear ratios and betting odds — anywhere two quantities need comparing in their simplest proportion.
Frequently asked questions
How do I simplify a ratio?
Divide both numbers by their greatest common divisor. 1920:1080 both divide by 120, giving 16:9.
What is the decimal of a ratio?
Divide the first number by the second. 16:9 is 16 ÷ 9 ≈ 1.778.
What is an aspect ratio?
An aspect ratio compares width to height, such as 16:9 for widescreen video or 4:3 for older screens. Enter the pixel width and height and the calculator reduces them to the familiar aspect ratio.
How do I scale a ratio up or down?
Multiply or divide both sides by the same number. To double a 2:3 mix you get 4:6, which still simplifies back to 2:3 — the proportion stays the same even as the quantities change.
Can I simplify a ratio with decimals?
The greatest-common-divisor method needs whole numbers, so if either value is a decimal the calculator shows the ratio and its decimal form without reducing it. Multiply both sides by 10 or 100 first to turn decimals into whole numbers.
What is the greatest common divisor?
It is the largest whole number that divides both values exactly. For 1920 and 1080 it is 120, so dividing each by 120 gives the simplest 16:9 form. The calculator finds it for you.
API — use this calculator from code
Call this calculator as a free JSON endpoint — no key required. Send the field values below as query parameters or JSON. Read the full API docs →
Endpoint
GET https://calculator.free/api/v1/ratio/curl
curl "https://calculator.free/api/v1/ratio/?a=1920&b=1080"JavaScript fetch()
const r = await fetch(
"https://calculator.free/api/v1/ratio/?" + new URLSearchParams({
"a": "1920",
"b": "1080"
}));
const data = await r.json();
console.log(data.results);Results are estimates for general guidance only, not financial, medical or tax advice.