📐 Aspect Ratio Calculator

How the ratio and the scaled size are worked out

The original width and height become a single decimal ratio, and everything else is built from that one number:

ratio = origWidth / origHeight
simplified = (origWidth / g) : (origHeight / g)   where g = gcd(origWidth, origHeight)
solvedHeight = newWidth / ratio
solvedWidth  = newHeight × ratio

With the defaults, 1920 / 1080 gives a ratio of 1.7778, and the greatest common divisor of 1920 and 1080 is 120, so the simplified ratio is 16:9. Ask for a new width of 1280 and the height comes back as 1280 / 1.7778 = 720.0. Fill in both new boxes instead and the tool compares newWidth / newHeight against the original ratio, calling it a match when the two differ by less than 0.001.

Filling the boxes

• Leave one of the two new fields empty. That empty box is the one being solved for. Filling both switches the tool from scaling to checking.
• Original width and height must both be above zero. A blank or zero original stops the calculation, because the ratio would be undefined.
• The scaled side is shown to one decimal place, so 1000 wide at 16:9 reads 562.5 high. Round it yourself before handing it to a renderer that wants whole pixels.

Frequently asked questions