So we all sit too much. That's not just some rhetoric about our modern working world. No, this is a fact that is definitely backed by science. If we're all sitting so much, we should be putting more thought into HOW we're sitting and yet, so many of us do it wrong. So what's the easiest way to determine if your desk and office chair are at the right heights for your spinal alignment? It's easier than you think.
Put a dot (a simple sticker or piece of tape will do the trick) in the center of the top 2/3rds of your computer screen. Now, adjust your desk and chair until your eyes are in an exact perpendicular line with this dot.
The same idea holds true if you prefer a standing desk. Add the dot to your screen and adjust your desk height, while standing in comfortable shoes, until your eyes are in the appropriate line of sight.