Glossary
Elbow height
The height of your relaxed, bent elbow, used as the reference point for setting desk and keyboard height correctly.
Elbow height is measured by standing or sitting normally, letting your arms hang relaxed at your sides, then bending them to roughly 90 degrees. Wherever your forearms land is your elbow height, and it is the single most useful number for setting up a desk. Get this one measurement right and most other adjustments follow from it.
The desk surface, or the keyboard tray if you use one, should sit at or just below elbow height so your wrists stay close to neutral while typing. Too high and your shoulders creep up toward your ears during long sessions. Too low and you end up hunching forward, which loads the lower back and neck. Standing desks and desk converters exist mainly to let you match this number in both the sitting and standing position.
A common mistake is setting desk height once while sitting and never rechecking it after switching chairs, changing shoes, or adjusting a standing desk. Chair seat height and desk height are linked, so if you raise or lower one you usually need to recheck the other against elbow height. People also confuse elbow height with countertop height, which is almost always too tall for typing comfortably.