Find a simplified aspect ratio, or calculate a missing width or height for any ratio
An aspect ratio describes the proportional relationship between an image's or screen's width and height, written as two numbers separated by a colon (e.g. 16:9). A 1920×1080 screen and a 1280×720 screen are both 16:9 — same shape, different size.
Width and height are divided by their greatest common divisor (GCD) to reduce them to the smallest whole numbers. For example, 1920×1080: the GCD of 1920 and 1080 is 120, so 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9, giving 16:9.
Keeping the same ratio when you resize stops photos and videos from looking stretched or squashed. When you're ready to resize the image itself, use our Image Resizer with Keep aspect ratio switched on.
Want a quick reference for common ratios? Read Common Aspect Ratios Explained: 16:9, 4:3, 1:1, and More on our blog.
Enter the image's width and height in pixels into the first calculator above — it returns the simplified ratio automatically.
Use the second or third calculator: enter the target ratio and either your known width or height, and the tool calculates the matching dimension that preserves the same proportions.
Both are widescreen, but 16:10 is slightly taller relative to its width than 16:9 — common on some laptop and monitor panels versus the 16:9 standard for TVs and most video.
No. All calculations happen entirely in your browser. The values you enter are never sent to our server or saved.