Aspect Ratio Calculator
Enter the ratio you want and one dimension. It gives you the other, and — the part most calculators leave out — it tells you what your rounding actually did to the ratio.
Why the rounding note matters
Pixels are integers, so most ratio conversions do not land exactly. 1920 at 2.39:1 gives 803.35 px — you have to pick 803 or 804, and either choice changes the real ratio slightly. Video encoders add a second constraint: dimensions usually have to be even, which can push you a further pixel away.
None of that matters for a wallpaper. It matters when you are matching two clips, or hitting a delivery spec with a tolerance. So this tool shows the resulting ratio and the error rather than quietly rounding and presenting the answer as exact.
Common ratios
| Ratio | Decimal | Typically used for |
|---|---|---|
| 16:9 | 1.778 | HD / UHD video, most displays |
| 9:16 | 0.563 | Vertical video, phone-first |
| 4:5 | 0.800 | Tall social post |
| 1:1 | 1.000 | Square |
| 4:3 | 1.333 | Older displays, many cameras |
| 3:2 | 1.500 | Most DSLR / mirrorless stills |
| 21:9 | 2.333 | Ultrawide |
| 2.39:1 | 2.390 | Anamorphic cinema |