Aspect ratio calculator
Reduce a width-to-height ratio and solve one matching dimension while preserving the source proportions.
Did this calculator give you what you needed?
What could be better?
The same multiplier on both axes
Proportional scaling applies one scale factor to width and height. Supplying one target dimension is enough to solve the other.
Ratio labels are shorthand
The reduced ratio is useful for comparison, while the decimal ratio is useful in calculations. Real layouts can use any proportional dimensions, not only familiar labels such as 16:9.
The ratios you will meet
Screens and video are 16:9, which is 1920 by 1080 and 3840 by 2160. Interchangeable-lens cameras shoot 3:2, the proportion inherited from 35 mm film, while phones and compacts usually shoot 4:3. Social posts favour 4:5 and 1:1, and cinema goes wider still at 1.85:1 and 2.39:1.
Mixing them is where images get quietly cropped. A 3:2 photograph placed in a 16:9 slot loses about 16% of its height, and the same photograph cropped to a square loses a third of its width. Deciding that crop yourself takes a minute; letting a template decide it is how heads end up cut off.
Frequently asked questions
How do I resize an image without distorting it?
Enter the source width and height, then give the one target dimension you know. The other is calculated from the same ratio, so both axes get the same scale factor. Any pair of numbers that comes from this page will hold the original proportions.
What aspect ratio is my photo?
Enter its pixel dimensions and read the reduced ratio. Most system cameras produce 3:2, most phones 4:3, and video frames 16:9. If the reduction gives something unfamiliar such as 683:512, the image has already been cropped or resized off its original proportions.
Why does A4 not reduce to a tidy ratio?
Because the A series is built on the square root of two, about 1.414, which is not a ratio of whole numbers. That is the property that lets A4 fold into two A5 sheets of the same shape. Reduced from millimetres, 210 by 297 comes out as 70:99, which is an approximation rather than the definition.
What is the difference between 16:9 and 16:10?
16:10, sometimes written 8:5, is noticeably taller: 1.6 against 1.778. It survives on laptops and monitors sold for document work because the extra height shows more of a page. Video is 16:9, so a 16:9 film on a 16:10 display gets thin bars above and below.
How much do I lose cropping between ratios?
Enough to plan for. Going from 3:2 to 4:5 for a social post costs 47% of the width; going from 16:9 to 1:1 costs 44%. Frame the original with the crop in mind, and check the result rather than trusting an automatic centre crop, which knows nothing about where the subject is.