When determining the heights of your chair, keyboard, desk, and monitor; start off at your feet and work up. Make sure your feet are flat on the floor then adjust your chair height so your knees and hips are at 90 degrees of flexion. You will not require a foot rest because your feet will be resting comfortably and there will be no pressure on your thighs. Place your keyboard and mouse at the height where your elbows are bent at 90 degrees of flexion and your upper arms are hanging freely from your shoulder joints. Usually desk surfaces are too high and a keyboard and mouse tray is needed to do this, unless you have an adjustable desk. If you do a lot of paperwork, you will need a desk surface approximately 2 inches higher than your elbow. Finally adjust your monitor to accommodate your natural gaze (See Monitor Height).