Aspect Ratio Calculator
Turn any width × height into its simplest ratio, or lock a ratio and resize so the other dimension follows automatically and your image, video, or layout keeps its proportions. Results update as you type, and nothing is uploaded.
Find the ratio of a size
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Enter a width and height to see the ratio.
Resize at a fixed ratio
Edit either the width or the height — the other side updates to keep the selected ratio.
How to use the aspect ratio calculator
There are two tools on this page. Use the first when you have a size and want to know its ratio, and the second when you have a ratio and want a matching size.
Find the ratio of a size. Type a width and height — say 1920 and 1080 — and you'll see the simplified ratio (16:9) instantly. It works for any units: pixels, millimetres, or arbitrary numbers.
Resize at a fixed ratio. Pick a ratio (or choose Custom and type your own), then enter a new width or a new height. The other dimension fills in automatically so the proportions never change and nothing gets stretched.
Everything runs in your browser — the numbers you type are never uploaded.
Common aspect ratios
- 16:9 — widescreen video, YouTube, and most TVs, monitors, and phones in landscape. Examples: 1280×720, 1920×1080, 3840×2160.
- 4:3 — older displays, many tablets, and a lot of point-and-shoot photos. Examples: 800×600, 1024×768.
- 1:1 — square, common for profile pictures and many social posts.
- 3:2 — the native ratio of many digital cameras and 35mm film.
- 21:9 — ultrawide monitors and cinematic video.
- 9:16 — vertical video for stories, reels, and shorts.
Aspect ratio questions
What is an aspect ratio? It's the proportional relationship between width and height, written like 16:9. It describes shape, not size, so the same ratio covers many different pixel dimensions.
How do I work out the aspect ratio of an image? Divide the width and height by their greatest common divisor. 1920 and 1080 both divide by 120, which gives 16:9. The first tool above does this for you.
How do I resize without distorting? Keep the same ratio. Lock the ratio, enter the new width, and use the height the calculator gives you so the image isn't stretched.
What is 16:9 in pixels? 16:9 is a shape, not a fixed size. Common 16:9 sizes are 1280×720, 1920×1080, and 3840×2160. Enter a width with 16:9 locked to get the exact matching height.
This calculator is a general tool for screen, photo, and video sizing — there's no rounding beyond two decimal places on the resized dimension.