Aspect Ratio Calculator

Aspect ratio is the ratio of width to height, used to describe the format of monitors, TVs, videos, and images. Common examples are 16:9, 4:3, and 21:9.

Enter the width/height resolution (pixels) to reduce it by the greatest common divisor and calculate the simplest aspect ratio. Useful for video editing or checking display specifications.

For example, a 1920×1080 resolution has a 16:9 aspect ratio.

Aspect Ratio Calculator Calculation Method

Divide the width and height by their greatest common divisor to express the simplest integer ratio.

The aspect ratio is 0 : 0 .

About This Calculator

Aspect ratio describes the proportional relationship between an image or video's width and height, reduced to its simplest form — 16:9 for widescreen, 4:3 for older displays, 1:1 for square social posts.

Enter any width and height in pixels to get the reduced ratio, plus the closest common ratio.

Aspect ratio is width divided by height, reduced to the smallest whole numbers: 1920 × 1080 reduces to 16:9 and 1080 × 1350 reduces to 4:5. Every platform publishes the ratios it prefers, and uploading a different one either crops the image or adds bars. To keep the ratio while resizing, scale both sides by the same factor — from a 1280 width, 16:9 gives 1280 × 720.

Key Formula:Ratio = width : height (divided by GCD)

Frequently Asked Questions

What are the most common aspect ratios?

16:9 is standard for widescreen video and most monitors, 4:3 for legacy television and some tablets, 21:9 for ultrawide, and 1:1, 4:5 and 9:16 for social media posts and vertical video.

How do I scale an image without distortion?

Keep the width-to-height ratio constant: if one dimension is fixed, compute the other with the same ratio. A 1920×1080 image scaled to 1280 wide must be 1280 × 9/16 = 720 tall.

What happens if I upload a 4:3 photo to a 16:9 slot?

Either the sides are cropped or the image is letterboxed. Most platforms centre-crop, so the top and bottom of a portrait shot survive while the sides are lost. Upload at the target ratio to control the framing yourself.

How do I work out a missing dimension?

Cross-multiply. For 16:9 with a width of 1920 the height is 1920 × 9 / 16 = 1080. With a known height of 1080 the width is 1080 × 16 / 9 = 1920.

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Sources & last update

2026-10-19