Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Calculate an image's aspect ratio from its pixel width and height.
This tool calculates an image's aspect ratio -- simplified to its lowest terms via GCD reduction (e.g. 1920×1080 → 16:9) -- from its pixel width and height, and names it when it exactly matches one of seven built-in common ratios (1:1, 4:3, 3:2, 16:9, 21:9, 9:16, 2:3).
Enter the image's width and height in pixels. The simplified aspect ratio appears instantly.
The tool rounds both dimensions to whole numbers, finds their greatest common divisor using the Euclidean method, and divides each side by it. The result is shown as width colon height. If the simplified pair exactly matches one of a short built-in list, the tool also displays a friendly name beneath it. Both width and height must be greater than zero, otherwise you see a prompt to enter both dimensions.
Ratio = (width ÷ GCD) : (height ÷ GCD)
Important detail: the name only appears when the simplified ratio is an exact match to one of these. There is no tolerance or nearest-match logic in the code, so an image of 1920 by 1081 will show a large odd-looking ratio and no name. The existing description on this page mentions a closest common ratio for near-matches. In practice the tool shows the exact simplified ratio and names it only on an exact match.
A 1920 by 1080 image has a GCD of 120, so the ratio is 16:9 and it is labeled Widescreen/HD Video. A 4000 by 3000 photo has a GCD of 1000, giving 4:3. A 1080 by 1350 image simplifies to 4:5, which is a valid ratio that simply has no label in the list. A 1500 by 1000 image gives 3:2. A hypothetical 1200 by 630 social preview image has a GCD of 30, giving 40:21, a ratio that is close to but not exactly 2:1 and gets no name.
Non-integer inputs are rounded before the GCD is taken, so 1920.4 is treated as 1920. Orientation matters: a portrait image of 1080 by 1920 gives 9:16, while the same image rotated gives 16:9. Very unusual pixel sizes, such as those from a phone screenshot with a status bar, can simplify to large numbers like 1179:2556 because they share no common factor. That is correct, since the real proportion just is not tidy. For a rough comparison in those cases, divide width by height to get a single decimal and compare it with the decimal of the ratio you are aiming for. For instance 16 divided by 9 is about 1.78.
The tool works on the pixel dimensions you enter. It does not read a file, so if you are working from a photo, check its pixel dimensions in your operating system's file properties or in an editor first. The aspect ratio is independent of print size and DPI, so the same ratio can describe a tiny thumbnail and a huge poster file. Note that a ratio describes shape only. Two images with the same ratio still differ in sharpness if their pixel counts differ.
The tool shows the exact simplified ratio for your dimensions regardless -- it only adds a common name (like 16:9 Widescreen or 4:3) when the simplified ratio is an exact match for one of the seven built-in ratios; near matches are not named.
The dimensions share no meaningful common divisor, so the simplified ratio is large, and it is not on the list of named ratios. The tool only names exact matches.
No. The label only appears when the simplified result is exactly one of the seven listed ratios. Otherwise you see the exact ratio alone.
Yes. Dividing both by 270 gives 4:5, and the tool shows it that way, though it has no built-in name for it.
Yes. A landscape image and a portrait image with the same pixel numbers produce reversed ratios, such as 16:9 versus 9:16.