Chair height starts at the floor

Almost everyone sets their chair by their legs: sit down, adjust until the feet are flat, done.

Then they reach for the keyboard and find the desk is above their elbows, so they raise the chair back up, and now the feet dangle. Whichever way it goes, one end is wrong, and most people settle on the version that hurts less by lunchtime.

The reason it can’t be solved this way is that your desk is almost certainly not adjustable, and your chair is. Fixed desks are built to one height, chosen to suit the taller end of the range of people who might sit at one. So the chair’s job is to put your hands at the right height for that desk, and your feet then need their own solution.

That’s the whole order of operations, and it runs the opposite way to intuition.

What the chair is actually for

Two jobs, and the priority between them matters.

Job one: put your forearms level with the desk surface. When your hands are on the keyboard, your shoulders should be doing nothing. Not lifted, not braced. If the desk is above that height, your shoulders come up to meet it, and they stay up all day.

Job two: support your back and thighs without pressure points. Real, but secondary, because you can fix job two with the seat depth and the backrest, whereas job one has only one input.

So: set the chair for the hands. Deal with the feet afterwards.

The check

CHAIR HEIGHT — the check
  Sit fully back. Hands resting on the keyboard where you'd type.
  Let your shoulders go completely slack for a moment.

  · Shoulders stay where they were, forearms roughly level   → height is right
  · Shoulders visibly drop when you release them             → chair is too low
  · Wrists angled up to reach the keys, elbows below desk     → chair is too low
  · Elbows well above the desk, wrists dropping down          → chair is too high

The releasing-the-shoulders test is the useful one. If letting go changes anything, they were holding something, and they were holding it because the desk is above where your arms want to be.

Do this at the keyboard, not sitting empty-handed. An empty-handed chair check tells you about the chair; you need to know about the chair and the desk together.

Then deal with the feet

Having set the chair for your hands, look down. If your feet aren’t flat with your thighs roughly level, that’s now a separate problem with a separate fix — and the fix is not to move the chair.

What “wrong” feels like:

Feet dangling, or toes touching. Your thighs are carrying the weight of your lower legs, so there’s pressure along the front edge of the seat. You’ll notice it as a dead or hot feeling in the thighs after an hour, and you’ll notice yourself perching forward or hooking your feet on the chair base to relieve it. Perching means you’ve stopped using the backrest, which loses you job two.

Knees well above hips. Chair too low — but if the hands check said the height was right, this usually means the chair itself has bottomed out and the desk is unusually low, which is rarer.

The fix is a footrest, and a footrest is a box. A ream of paper. A stack of books. A shoebox with something solid in it. An upturned drawer. It needs to be stable, wide enough that both feet fit without aiming, and roughly the thickness of the gap. That’s it. Purpose-built footrests exist and they tilt, which is mildly nicer; the box does the actual job.

Get the height by trial: sit, put the object under your feet, and check that the pressure along the front of the seat is gone and your knees aren’t pushed up. Add or remove a book.

Seat depth and the backrest

Once height is settled, two adjustments that most people never touch.

Seat depth. Sitting fully back, there should be a gap between the front edge of the seat and the back of your knees — enough that the edge isn’t pressing into anything. Too deep and you can’t use the backrest without the edge digging in, so you slide forward and sit unsupported. Many chairs have a sliding seat pan; if yours doesn’t and it’s too deep, a firm cushion behind your back effectively shortens it.

Backrest height. The lumbar curve of the backrest wants to sit in the curve of your lower back, not above or below it. If it’s fixed and lands in the wrong place, a small rolled towel is the adjustment. This is genuinely one of the cheapest improvements available and it’s routinely ignored because it looks improvised.

Armrests: usually the problem

Armrests get set once at the factory and then blamed for nothing, when they’re often the reason shoulders won’t come down.

The rule: armrests should meet your arms where your arms already are, or get out of the way. If they hold your elbows higher than the desk, your shoulders are lifted by the chair itself. If they’re too low, they do nothing and you ignore them, which is harmless.

So if they’re adjustable, lower them until they just touch your relaxed elbows. If they’re fixed too high, and they are on a lot of chairs, the honest answer is to remove them if the chair allows it. Fixed high armrests also prevent you pulling the chair close enough to the desk, which pushes the keyboard away and makes you reach forward — one bad setting causing two compensations.

When the desk is the constraint

Sometimes the check fails in a way the chair can’t solve: chair at its lowest, hands still below the desk. The desk is too high for you and no chair adjustment will change that.

Options, cheapest first:

Lower the desk. Many desks have adjustable feet or a leg assembly with bolt holes at multiple heights. Look underneath before assuming.

Raise everything on the desk instead — no. This makes it worse, because your hands are already too high.

Add a keyboard tray, or work with the keyboard on your lap if the desk situation permits. Both put the hands below the desk surface where they need to be.

Accept it and raise the chair, then build a taller footrest. Perfectly workable, and it’s what most people end up doing. A tall footrest looks silly and works fine.

The reverse case — desk too low, hands below elbow height even at the chair’s lowest setting — is rarer and easier: raise the desk on blocks under the legs, making sure it’s stable.

What this doesn’t fix

Getting the chair right removes a reason to hold tension. It doesn’t make sitting still for four hours a good idea, and a well-adjusted chair that you don’t get out of will still leave you stiff. Changing position regularly is the other half, and it’s a different subject.

If you have persistent pain, numbness, tingling or weakness — particularly if it’s in one arm, or it wakes you up — that’s a reason to see a clinician rather than to keep adjusting furniture.

With the chair set, the next constraint in the chain is the screen: your hands are now in the right place, and your head will go wherever the monitor makes it go.