Calculate aspect ratios and scale dimensions proportionally. Presets for 16:9, 9:16, 4:3, 1:1 and Open Graph. Free, runs in your browser.
First time here? Pick a preset ratio, or type your own Your input is processed locally and disappears when you close the tab.
Getting a dimension wrong by a few pixels is how images end up stretched, letterboxed, or cropped badly by the platform you uploaded them to. This free aspect ratio calculator works in both directions so you can avoid it.\n\nGive it a ratio and one dimension and it fills in the other, which is what you need when resizing without distortion. Or paste an existing width and height and it reduces them to the simplest whole-number ratio, which is what you need when you are trying to work out what shape an asset already is.\n\nPresets cover the shapes that actually come up: 16:9 for video and most screens, 9:16 for Reels and Stories, 1:1 for square posts, 1.91:1 for Open Graph share images, and 3:2 for camera-native photography. Resolution shortcuts from 240p to 4K fill in standard heights instantly, and a live shape preview makes the proportion obvious.\n\nWhere a size does not reduce to small whole numbers the tool says so rather than showing something like 1358:1075 as though it were useful. Everything runs in your browser. Pair it with the Image Resizer to apply the dimensions, or the Open Graph Preview to check a share image renders correctly.
Pick a preset ratio, or type your own
Enter either a width or a height
The other dimension is calculated automatically
Or paste an existing size to find out what ratio it is
Editing either side recalculates the other. Presets keep width fixed.
Dimensions are rounded to whole pixels, so an exotic ratio can be a pixel off the exact figure — unavoidable, since you cannot have a fraction of a pixel.