Aspect Ratio Calculator

Find the aspect ratio of any width and height, or the missing side for a given ratio. The aspect ratio calculator has presets for 16:9, 4:3, 21:9, and other common formats.

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Aspect ratio
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How to use the Aspect Ratio Calculator

  1. Choose Ratio from a size or Missing side from a ratio.
  2. Enter the width and height, or pick a ratio and enter the one side you know.
  3. Press Calculate. You get the ratio or the new size, with a preview rectangle.

How it works

ratio = (width ÷ gcd) : (height ÷ gcd)
height = width × ratio height ÷ ratio width
width = height × ratio width ÷ ratio height

gcd is the greatest common divisor of the width and height, found with Euclid's algorithm.

Examples

  • 1920 × 1080: the gcd is 120, so the ratio is 16:9.
  • 16:9 at a width of 1280: height = 1280 × 9 ÷ 16 = 720.
  • 2560 × 1080 is exactly 64:27, which is sold as 21:9 ultrawide.

Common aspect ratios

  • 16:9: HD, 4K, most monitors and YouTube
  • 9:16: vertical video for Reels, TikTok, and Shorts
  • 4:3: older TVs and iPads
  • 3:2: many camera sensors and Surface laptops
  • 16:10: many laptops, such as 1440 × 900
  • 1:1: square posts

Limitations

  • Decimal sizes are shown as a ratio to 1, such as 1.7778:1.
  • Resized sides may not be whole pixels; the rounded size is shown too.

Frequently asked questions

What aspect ratio is 1920 × 1080?

16:9.

How do I calculate aspect ratio?

Divide the width and height by their greatest common divisor.

What is the height of 16:9 at 1280 wide?

720 pixels.

Often used together with the Aspect Ratio Calculator.