Aspect Ratio Calculator
Reduce a width and height to a simple ratio.
Results update as you type.
How it works
An aspect ratio calculator reduces a width and a height to the simplest whole-number ratio that describes their proportion, such as turning 1920 by 1080 into a clean 16:9. It also reports the decimal equivalent, the width divided by the height, which is handy for sorting or comparing shapes numerically. Aspect ratio captures the shape of a rectangle independent of its actual size, so a phone thumbnail and a cinema screen can share the same ratio. This matters across photography, video, web design, and print. Matching aspect ratios keeps images from being stretched or cropped unexpectedly when they move between a camera, a layout, and a display. Knowing the ratio helps you pick the right export preset, design responsive layouts, and choose media that fills a screen without letterboxing or distortion. The calculation works by finding the greatest common divisor of the two dimensions and dividing both by it, which reduces the fraction to its lowest terms while preserving the exact proportion. Common results like 16:9, 4:3, 3:2, and 21:9 correspond to familiar screen and photo formats. Designers, photographers, video editors, and developers use an aspect ratio calculator to keep proportions consistent and avoid the awkward stretching that follows a mismatched ratio.
ratio = width ÷ gcd : height ÷ gcd
An aspect ratio is width divided by height expressed in the smallest whole numbers. Dividing both dimensions by their greatest common divisor, the largest number that goes evenly into each, reduces the pair to that lowest form without changing the proportion. For example, 1920 and 1080 share a divisor of 120, giving 16:9. The decimal value is simply width divided by height, useful for direct comparison.
Source:Standard digital media
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Worked example
How to use this calculator
- 1
Enter your values
Enter width and height.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Aspect ratio updates instantly as you type — no button to press.
Frequently asked questions
What is an aspect ratio?
An aspect ratio describes the proportional relationship between a rectangle's width and its height, written as two numbers separated by a colon, such as 16:9. It captures shape rather than size, so any 16:9 image has the same proportions whether it is a tiny thumbnail or a huge television. Knowing the ratio lets you scale, fit, and compare images and screens without distorting them.
How is the ratio simplified?
The calculator finds the greatest common divisor of the width and height, the largest whole number that divides both exactly, then divides each dimension by it. This reduces the pair to its smallest whole-number form while keeping the proportion identical. For 1920 by 1080 the divisor is 120, producing 16:9. Simplifying this way gives the familiar ratios people recognise instead of unwieldy large numbers.
What are common aspect ratios?
Widespread ratios include 16:9 for modern televisions and most online video, 4:3 for older displays and some tablets, 3:2 for many still cameras and prints, 1:1 for square social media posts, and 21:9 for ultrawide monitors and cinematic film. Recognising these helps you choose export settings and crops that match your target display or platform without introducing black bars or stretching.
Why does the decimal value help?
The decimal ratio, width divided by height, gives a single number you can compare directly, which is useful when two ratios look similar. For instance, 16:9 is about 1.78 and 16:10 is 1.60, so the decimals make the difference obvious. It is also handy in code and spreadsheets, where a numeric value is easier to sort, filter, or calculate against than a colon-separated pair.
What if my numbers do not reduce neatly?
Some dimensions share no large common divisor and reduce to an unusual ratio with big numbers, which simply means the shape does not match a standard format. That is normal for arbitrary crops. You can still use the decimal value to compare it against common ratios, and if you need a standard shape, adjust the width or height slightly until it reduces to a familiar ratio like 16:9.