A standing desk converter transforms a normal desk into a standing desk. These converters sit on top of your existing workspace, providing a new surface to put your monitor, keyboard, and mouse on. They have a mechanism that can raise or lower them, usually either a pneumatic lift or electric, allowing you to work while sitting or standing. 

If you're working at a standing desk converter, your monitor should be right in front of your eyes. Your keyboard should be at a height where you can type without holding your arms up or down — essentially, 90 degrees out from your elbows. The height you need from your standing desk converter will depend on how tall you are and how tall your existing desk is, so you may need to pull out the measuring tape before ordering. BTOD has a handy guide to figuring work surface heights.