Aspect Ratio Calculator

Ratios that do not reduce neatly

Many screens are sold under a rounded name. 1366 × 768 reduces to 683:384, which is close to but not exactly 16:9, and 2560 × 1080, marketed as 21:9, is really 64:27. 3440 × 1440 comes out as 43:18. 1920 × 1200 reduces to 8:5, the same shape as the 16:10 name it goes by. An odd-looking result usually means the size is a near miss, and fitting it into an exact 16:9 frame will leave thin bars or need a small crop.

Rounding the scaled size

The scaled height can come out fractional, such as 1080 × 607.5 for a 16:9 frame at a width that does not divide evenly. Pixels are whole, so round it, and for video round to an even number: the H.264 and H.265 encoders used for most MP4 files typically reject odd dimensions with ordinary 4:2:0 color. For 16:9, a target width that is a multiple of 32 always gives a whole, even height. Apply the size with the image resizer.

How to use it

1. Enter the original width and height.
2. Add a target width.
3. Read the reduced ratio and target height.

Privacy & limitations

All arithmetic is local. Fractional source dimensions are rounded for ratio reduction.