Free tool · No sign-up

Aspect Ratio Calculator

Enter a width and height to get the simplified aspect ratio (like 16:9), then type a new width or height and this calculator finds the other side that keeps the same proportions — so nothing gets stretched. It runs entirely in your browser: free, instant, and no sign-up.

Start from a common ratio

WidthHeight

Enter a width and height, or pick a ratio above, to see the simplified aspect ratio.

Resize keeping this ratio — fill one side, get the other

New widthNew height

Runs entirely in your browser — nothing you enter is uploaded.

Frequently asked questions

Divide the width by the height and simplify the fraction to its lowest terms. For example, 1920 × 1080 reduces to 16:9 because both numbers share a common factor of 120. Enter any width and height above and this calculator shows the simplified ratio and the decimal instantly.

Keep the same width-to-height ratio. Enter your original width and height, then type the new width (or height) you want, and the tool fills in the matching value for the other side — so the proportions stay identical, with no stretching or squashing.

16:9 is standard widescreen for YouTube, TVs, and most monitors; 1:1 is square, common for social posts; 9:16 is vertical for Reels, Stories, and TikTok; 4:3 and 3:2 are common in photography; and 21:9 is ultrawide. Use the preset buttons to start from any of these.

Yes — free, no sign-up, and every calculation runs in your browser, so nothing you enter is uploaded.