Aspect Ratio Calculator
Type any two of width, height and ratio — the third updates instantly. Includes a live visual preview rectangle and presets for every common video, photo and print format.
How to use this aspect ratio calculator
- Set the ratio (e.g. 16:9) using the inputs or pick a preset.
- Type a width — the height updates to match the ratio.
- Or type a height — the width updates instead.
- Click 'Detect ratio' to compute the simplified ratio from your dimensions.
- Copy the CSS aspect-ratio property or the dimensions string.
Frequently asked questions
What is 16:9?
16:9 is the standard widescreen ratio for HD/4K video, YouTube, most TVs and laptops. 1080p = 1920×1080. 4K UHD = 3840×2160.
How does 'Detect ratio' work?
It simplifies your width × height to the smallest equivalent integer ratio using GCD. So 1920×1080 becomes 16:9.
What's the CSS aspect-ratio property?
It's the modern way to lock an element's shape. `aspect-ratio: 16 / 9` makes the element keep that ratio whatever its width.
Why does my video render with black bars even though my project is 16:9?
Your project canvas is 16:9 but the source clip might be 4:3 or vertical. Editors letterbox the mismatch by default to preserve every pixel of the source. To fill the frame, either crop the source to match 16:9 or use a 'fill / cover' scaling mode (which crops automatically).