How this calculator works
Seated office work is set up around the elbows. The chair goes high enough that the feet rest flat on the floor with the knees near a right angle, and the desktop then sits level with the undersides of the elbows bent to about 90 degrees. CCOHS guidance puts the optimal seat height at roughly one quarter of body height. Sitting elbow height above the seat adds about 0.15 of body height, which puts the working surface at about 0.40 of standing height. Both results are starting points for an adjustable chair and desk, not a precise prescription: leg length, torso length and footrest use all move the right answer by a few centimetres.
Formula
seat height = 0.25 x body height. desktop height = seat height + 0.15 x body height = 0.40 x body height. For 175 cm this gives 43.8 cm and 70.0 cm.
Worked example
A person 175 cm tall in shoes gets a seat height of 43.8 cm and a desktop at 70.0 cm. A shorter colleague at 160 cm gets 40.0 cm and 64.0 cm, which is why a single fixed 74 cm desk suits neither of them well without a footrest or an adjustable platform.
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Frequently asked questions
Why is the desktop below the usual 74 cm office desk?
Fixed desks around 74 cm suit people near 185 cm. For shorter workers a 74 cm surface lifts the shoulders and bends the wrists upward, so the elbow rule gives a lower number, and an adjustable desk or keyboard tray is the fix.
Should I include shoe heel height?
Yes. Measure in the shoes you actually wear at the desk. A 3 cm heel raises the seated elbow height and the recommended surface with it.
What if my chair cannot reach the seat height?
Set the chair so your feet rest flat and the knees are near 90 degrees, then adjust the desk to your elbows or add a footrest. Feet dangling is the problem to avoid, because it loads the thighs and lower back.
Does this cover standing desks?
No. Standing work uses a higher surface, roughly 0.63 of body height. Use the standing desk height calculator for that number.