Aspect Ratio Calculator
Find width or height from a ratio.
Pick an aspect ratio (or enter a custom one) and a width or height to instantly get the matching dimension. Useful for images, videos, thumbnails and social media assets. Everything runs locally in your browser.
:
Your input is processed locally in your browser — nothing is uploaded, stored or logged.
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How it works
- 1 Choose a ratio, or enter a custom one.
- 2 Type a width or a height.
- 3 The matching dimension is filled in automatically.
Common use cases
- Size a 16:9 video or thumbnail.
- Fit images to a social media ratio.
- Plan a 21:9 banner.
- Resize while keeping proportions.
Frequently asked questions
Is my input sent to a server?
No. Every calculation runs locally in your browser — your input is never uploaded, stored or logged.
How is the missing side calculated?
From the ratio: height = width × ratioH ÷ ratioW (and the reverse). For 16:9, a width of 1920 gives a height of 1080.
Can I use a custom ratio?
Yes — choose Custom and enter any width:height ratio.
Is it really free?
Yes — free, with no signup and no limits.