Aspect Ratio Calculator
Resize without distortion — give three numbers, get the fourth.
How it works
Aspect ratio is width divided by height, and preserving it means scaling both dimensions by the same factor. Fix one and the other follows.
The ratio itself is usually quoted in lowest terms, found by dividing both numbers by their greatest common divisor: 1920 x 1080 reduces to 16:9. Some awkward ratios are conventionally left un-reduced — 1.85:1 and 2.39:1 in cinema — because the reduced integer form is unwieldy.