Aspect Ratio Calculator

How to Use the Aspect Ratio Calculator

Select the calculation you need and enter the relevant dimensions or aspect ratio.

Choose a calculation — Select Calculate Ratio, Calculate Width or Calculate Height.
Enter the dimensions — Provide the known width and height, or enter the known dimension and required aspect ratio.
Enter the aspect ratio when required — Use the width:height format, such as 16:9 or 4:3.
Calculate the result — Select the appropriate calculation button to display the simplified ratio or missing dimension.

How to Calculate Aspect Ratio

An aspect ratio expresses the relationship between width and height using two numbers separated by a colon. To simplify a pair of dimensions, divide both numbers by their greatest common divisor. For example, a 1920 × 1080 image has a greatest common divisor of 120, producing an aspect ratio of 16:9.

When resizing content, the same proportion must be maintained. If an image has a 16:9 aspect ratio and its width is changed to 1280 pixels, the corresponding height is 720 pixels. The calculator uses the same proportional relationship to determine missing dimensions.

Common Aspect Ratios

Common aspect ratios include 1:1 for square content, 4:3 for some traditional displays and image formats, 16:9 for widescreen video and displays, and 21:9 for some ultrawide displays and cinematic applications. The appropriate aspect ratio depends on the content and the target device or platform.

Aspect Ratio and Image or Video Resolution

Aspect ratio and resolution describe different properties. Resolution specifies the actual dimensions, such as 1920 × 1080 pixels, while aspect ratio describes the proportional relationship between those dimensions. Multiple resolutions can therefore share the same aspect ratio. For example, 1280 × 720 and 1920 × 1080 are both 16:9.

Aspect Ratio Calculation Notes

The calculator accepts positive numerical dimensions and can be used with pixels, physical measurements or other consistent units. If the width and height use the same unit, the resulting aspect ratio remains valid regardless of which unit was used.

When resizing an image or video, calculated dimensions may contain decimals. If the final medium requires whole pixels, rounding may be necessary. Rounding can introduce a very small difference from the mathematical ratio, so dimensions should be checked against the requirements of the target platform or format.

Frequently Asked Questions

What is an aspect ratio?

An aspect ratio describes the proportional relationship between the width and height of an image, video, screen or other rectangular area. It is normally written as width:height, such as 16:9 or 4:3.

How do you calculate an aspect ratio?

To calculate an aspect ratio, divide the width and height by their greatest common divisor and express the resulting whole numbers as width:height. For example, 1920 × 1080 simplifies to 16:9.

What is the most common aspect ratio for widescreen video?

16:9 is a widely used widescreen aspect ratio for television, online video, computer displays and many modern devices.

How do I resize an image without changing its aspect ratio?

Keep the original width-to-height ratio when changing dimensions. Enter the known dimension and the original aspect ratio into the calculator to determine the corresponding dimension.

What is the difference between aspect ratio and resolution?

Aspect ratio describes the proportional relationship between width and height, while resolution describes the actual number of pixels or other units in those dimensions. Different resolutions can share the same aspect ratio.

Can this aspect ratio calculator work with any dimensions?

Yes. The calculator can work with positive width and height measurements regardless of whether they represent pixels, inches, centimetres or another consistent unit. The units themselves do not affect the ratio.

Aspect Ratio Calculator