Aspect Ratio Calculator

It finds the greatest common divisor (GCD) of the width and height in pixels, then divides both numbers by that GCD to get the smallest whole-number ratio that represents the same proportion. A 6000 by 4000 pixel image has a GCD of 2000, so dividing both dimensions by 2000 gives 3:2 -- the same ratio however large or small the original pixel dimensions were, as long as the proportion between them stays the same.

Decimal ratio is width divided by height, so raising the width by a given percentage raises the ratio by roughly the same percentage, while raising the height by the same percentage lowers the ratio, because height sits in the denominator of the division. The two inputs pull the ratio in opposite directions, which is exactly what makes aspect ratio a relationship between the two dimensions rather than a property of either one alone.

The ratio reduces to exactly 1:1 and the decimal ratio equals 1.0, with orientation reported as square rather than landscape or portrait. This is the single dividing line in the calculator's orientation logic -- any width greater than height reports landscape, any height greater than width reports portrait, and only an exact match reports square.

No -- the crop dimensions are always calculated to fit within the original width and height, using the smaller of the two possible crop dimensions at each step. If an image is already close to 16:9, the suggested crop will be very close to the original size; if it's far from 16:9 (a very square or very elongated image), the crop will need to discard a much larger share of the original frame to reach that ratio.