Aspect Ratio Calculator
Convert between width × height and aspect ratio (16:9, 4:3, 21:9, …) — fit any ratio inside a container.
Presets
1920 × 108016:9
Fit inside container
Largest size of this ratio that fits in the container without cropping.
Scaled to: 1280 × 720
How to use
- Pick a preset, or type any width/height/ratio — the others update automatically.
- Optionally enter a container size to see the scaled-to-fit dimensions.
- Copy the result string.
About this tool
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Three linked fields — width, height, and ratio — that keep each other consistent: type a new width and the height follows, type a new ratio in any of the usual notations and the height adjusts to match. Ratios are reduced by their greatest common divisor, which is honest rather than flattering: 1920×1080 shows as 16:9, but a 1366×768 laptop screen shows as 683:384, because it genuinely is not 16:9. Eight presets cover the common video and social formats. The fit-inside section answers the other everyday question — given a 1280×800 container, how large does a 16:9 video actually render? — by comparing the two ratios and constraining whichever side runs out first, the same letterboxing a video player does.
Frequently asked questions
Why does the ratio get reduced to '8:5' instead of '16:10'?
The tool divides both sides by the greatest common divisor — 16:10 and 8:5 are the same shape. Both are correct.
Which separators does the ratio input accept?
:, ×, x, and / — 16:9, 16×9, 16x9, 16/9 all work.
What does 'fit inside' compute?
Given a container W × H and your aspect ratio, the largest dimensions of that ratio that fit inside without cropping or stretching.
Decimals?
Yes — 2.39:1 (cinema scope) is parsed correctly.
Why doesn't my 1366×768 laptop show 16:9?
Because it genuinely is not 16:9. Reduced by its greatest common divisor it is 683:384, or about 1.779 against 16:9's 1.778 — close enough for marketing to round, not close enough for the arithmetic to agree.
What is the difference between fitting inside and cropping?
Fitting scales the whole image down until it sits inside the container, leaving bars on two sides. Cropping fills the container and cuts whatever hangs over the edge. This tool computes the first.
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