How many hours does it take to cross stitch?

The main consideration is the complexity of the pattern, whether there are solid colors, 'confetti stitching' with alot of color changes and fractional stitches versus whole stitches. And the other consideration is the experience of the stitcher.

One way is to time yourself on a 10 x 10 block of stitches. If you need 30 minutes to stitch a block of 100 stitches, then you are capable of completing 200 stitches per hour.

Use this pattern as an example - the stitch count is 89 x 51 (4,539 stitches). If your average stitching time is 200 stitches per hour, then the total project is about 22 hours (4,539/200).