How the chair setup calculator works
Five settings, in order
- Seat height = floor-to-knee-crease (elbows at desk height when seated; feet flat). This is the master adjustment — everything else follows it.
- Seat depth ≈ butt-to-knee minus 2–4 cm — two to three finger-widths behind the knees. Too deep forces slouching or perched sitting; too shallow cuts thigh support.
- Armrests = seated elbow height minus desk height, if positive — support forearms lightly, shoulders hanging. If armrests collide with the desk, lower them or drop them entirely; desk-colliding armrests are a shoulder-shrug machine.
- Backrest angle ~100–110° with lumbar support at the belt line — upright 90° loads the spine more than slight recline.
- Footrest — if seat height (fitted to the desk) leaves feet dangling, a footrest completes the chain. Height = the gap under your feet.
The desk was never adjustable — the chair is
The calculator detects the classic conflict: desk fixed at 73–75 cm, body smaller than the desk's designer. The resolution order is chair up to meet the desk, footrest to complete the leg posture, monitor riser to restore eye line. This chain fixes more "bad back" reports than any $1,500 chair — a $150 chair correctly fitted beats a premium chair at factory defaults every time.
After the numbers
Fit is verified by an hour of work: feet flat and supported, thighs roughly parallel, shoulders hanging, elbows floating or lightly supported, low back contacted. One setting off (usually depth) announces itself within the hour — adjust ±1–2 cm and re-test. Chairs have more marketing than moving parts; the five above are the ones that matter.