Aspect Ratio Calculator

Find the aspect ratio of any width and height — 1920 × 1080 is 16:9 — see the closest standard ratio, and calculate a new width or height that keeps the proportions. Includes common sizes for the ratio, from 320 px to 4K.

This tool runs entirely in your browser.

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How to use the Aspect Ratio Calculator

1Enter the width and height in pixels — the maths works the same for any unit.
2Read the simplified ratio, the decimal ratio and the closest standard.
3To resize, enter a new width or a new height (if you fill both, the new width is used) and get the matching other side.

What is the Aspect Ratio Calculator?

The aspect ratio is width ÷ height reduced to whole numbers by their greatest common divisor: 1920 and 1080 share 120, giving 16:9. Screens sold as 21:9 are really 64:27 (2.37:1) and cinema formats like 2.39:1 are given as decimals.

When resizing, the new height is new width × height ÷ width (or the new width is new height × width ÷ height), rounded to whole pixels. The table shows which common widths divide evenly for the ratio, which avoids blurry half-pixel scaling.

Frequently asked questions

What aspect ratio is 1080 × 1920?

9:16 — the same as 16:9 turned to portrait, used for phone videos, Stories and Reels.

Why does my monitor say 21:9 but the calculator says 64:27?

“21:9” is a marketing name. 2560 × 1080 is exactly 64:27 (2.37:1), which is close to 21:9 (2.33:1).

Is the Aspect Ratio Calculator free and private?

Yes. The Aspect Ratio Calculator is free, needs no account, and runs entirely in your browser. What you type is never sent to a server or stored.

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