Aspect Ratio Calculator

Simplify any width × height to its aspect ratio (16:9, 4:3, 21:9...) and compute the matching height for a new width. Instant.

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How it works

Ratio = width ÷ GCD(width, height) : height ÷ GCD(width, height). New height = new width × original height ÷ original width — proportions stay identical

Examples

InputOutput
1920 × 108016:9
1280 wide of 1920×1080720 px tall
1024 × 7684:3

Frequently Asked Questions

How do I calculate an aspect ratio?

Divide both sides by their greatest common divisor: 1920×1080 → GCD 120 → 16:9. This calculator does that instantly and also scales to a new width.

What aspect ratio should video be?

YouTube and TV: 16:9. Instagram Reels/TikTok/Shorts: 9:16 vertical. Cinema scope: 21:9. Instagram feed posts: 1:1 or 4:5.

Why does my resized image look stretched?

The width and height were scaled by different factors. Keep the same ratio — enter the new width above and use the computed height, never round it independently.

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