Aspect Ratio Calculator
Enter width and height to simplify the aspect ratio, or lock a ratio and calculate the missing dimension.
Keep media and layouts proportional
Aspect ratio is the proportional relationship between width and height — 16:9 for most video, 4:3 for classic photos, 1:1 for square social posts. Get it wrong and images stretch, videos letterbox awkwardly, and cards in a grid end up different heights. This calculator works both ways: enter a width and height and it reduces them to the simplest whole-number ratio, or type a target ratio to lock it and instantly get the height that matches your current width.
That makes it handy for a lot of everyday jobs — sizing a hero image to 16:9, working out the height of a
responsive embed, checking that a thumbnail set shares one ratio, or generating the value for the modern CSS
aspect-ratio property so a container reserves the right space before its media loads.
Private and instant
All the math runs locally in your browser — nothing is uploaded, and the ratio updates the moment you change a value.
Frequently Asked Questions
What is aspect ratio?
Aspect ratio is the proportional relationship between width and height, such as 16:9, 4:3, or 1:1.
Can I calculate a missing dimension?
This version simplifies the ratio from width and height; use the simplified ratio to resize proportionally.
Where is this useful?
Images, videos, cards, thumbnails, embeds, and responsive layout blocks.
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