Aspect Ratio Calculator

Calculate dimensions that keep the same aspect ratio. Free online tool for images, video, and screens. No signup, instant results.

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Frequently asked questions

What is a common aspect ratio?
16:9 (widescreen HD), 4:3 (classic TV), 21:9 (ultrawide cinema), 1:1 (Instagram square), 9:16 (vertical portrait/reels).
How does the tool simplify the ratio?
It divides both width and height by their greatest common divisor (GCD). 1920×1080 → GCD 120 → 16:9.
Why does my image look stretched?
Your new dimensions don't match the original aspect ratio. Use this tool to calculate the matching height for any width (or vice versa).
What is aspect ratio in videos?
The width-to-height ratio of the frame. 16:9 is YouTube default. 9:16 is vertical mobile (TikTok, Instagram Reels). 4:5 is Instagram feed.