Aspect Ratio Calculator

About

Enter a width and height to get the aspect ratio in lowest terms (1920×1080 is 16:9), its common name and the decimal value. Then type a new width or height to get the other side at the same ratio, rounded to whole pixels.

How is the ratio worked out?

Both sides are divided by their greatest common divisor, so 1920×1080 becomes 16:9. Decimals are scaled up to whole numbers first.

Why does 1366×768 say "≈ 16:9"?

Its exact ratio is 683:384, which is within 1% of 16:9. Many screen sizes are like that, so near misses get the common name with a ≈ and the exact ratio next to it.

What happens when the new size isn't a whole number?

It's rounded to the nearest pixel, and the tool says so when rounding makes the result slightly off the exact ratio.