Aspect Ratio Calculator

Ratios and where each comes from

An aspect ratio is width to height reduced to its simplest form. 1920 by 1080 is 16:9. 3000 by 2000 is 3:2. 1080 by 1080 is 1:1.

The common ones have histories. 3:2 comes from 35mm film. 4:3 from early television and computer displays. 16:9 from a compromise between cinema formats when widescreen television was standardised. 1:1 from medium format and, more recently, from Instagram.

Knowing the ratio matters because content designed for one and displayed in another gets cropped or letterboxed, and which parts survive is determined by where the important content sits.

Resizing without distortion

Changing one dimension requires changing the other proportionally, and the calculation is a simple proportion: new width times original height divided by original width.

Failing to do this stretches the image, which is immediately visible on anything containing faces, circles or text. It is one of the few image errors that reads as obviously wrong to everyone rather than only to designers.

Most software maintains the ratio by default with a lock that can be released, and most distortion happens because someone released it deliberately to make something fit. The correct fix is cropping rather than stretching.

Cropping between ratios

Moving from one ratio to another means losing content from two edges, and how much depends on how far apart the ratios are.

Going from 3:2 to 1:1 loses a third of the width. From 16:9 to 4:3 loses a quarter. From 4:3 to 16:9 loses a quarter of the height.

Composing with the eventual crop in mind is what makes this manageable. Photographers shooting for social media frequently frame with a square crop in mind while capturing 3:2, leaving room on both sides. The alternative is discovering that the subject's head is outside the square.

Ratios for the platforms

Social platforms each have preferences and they change, which makes any list a snapshot rather than a reference. The stable pattern is that feeds favour vertical or square and video favours vertical.

The practical approach is to capture wide and crop rather than to shoot for one platform. A 3:2 or 4:3 capture with the subject centred crops acceptably to square, to 4:5 and to 9:16.

Where a single asset must serve several ratios, designing with a safe area is the standard technique: keep everything important within a central region that survives every crop, and treat the edges as expendable.

Video, and the awkward legacy cases

Video adds pixel aspect ratio, which is separate from the frame aspect ratio. Some legacy formats used non-square pixels, so a frame of 720 by 480 could display as 4:3 or 16:9 depending on the pixel shape.

Modern formats use square pixels and the complication largely disappears, though it survives in archive footage and in some broadcast workflows.

The symptom is video that looks horizontally stretched or squashed when imported into software that guessed the pixel aspect ratio wrong. It is a setting rather than a damage, and it is fixable by telling the software the correct interpretation.

Where several ratios have to be served from one shoot, the cheapest solution is a shot list rather than a crop. Capturing the same subject twice, once composed for a horizontal frame and once for a vertical, takes seconds at the time and produces two properly composed images instead of one image and one compromise. Photographers who work regularly for social media do this as standard, and it is consistently better than any amount of clever cropping afterwards.