Does your chair actually fit you? Three tests, thirty seconds

“Ergonomic” is not a property a chair has. It is a relationship between a chair and a body, and the same chair can be excellent for one person and actively harmful for the person sitting next to them.

Which means the useful question is never “is this a good chair”. It is “does this chair fit me”. Here is how to find out, using the chair you already own, right now.

Test 1: the two-finger test (seat depth)

This is the one almost nobody checks, and it is the one that matters most.

Sit all the way back so your back touches the backrest. Feet flat on the floor. Now slide two fingers into the gap between the front edge of the seat and the back of your knee.

• The seat presses into the back of your knee, no gap. The seat is too deep for your femur length. You cannot sit back properly, because sitting back hurts. So you sit forward, away from the backrest, unsupported, and slump. Every “I keep slouching no matter what” problem I have ever looked at was this.
• A gap wider than about four fingers. Seat too shallow. Your thighs are unsupported and your weight concentrates on a small area.
• Two to three fingers. Correct. Move on.

If your chair has a seat-slide lever, you can fix this in ten seconds and you have been sitting on an adjustable chair without adjusting it, which is extremely common. If it does not, this is the single best reason to replace the chair.

Test 2: feet and knees (seat height)

Feet flat on the floor, knees at roughly a right angle, thighs roughly parallel to the ground.

If your feet dangle, the chair is too high, and the front edge of the seat is now cutting into the underside of your thighs. Lower it. If the chair does not go low enough — common for anyone under about 5’4” — a footrest is a legitimate patch, but understand that it is a patch for a chair that does not fit.

If your knees are higher than your hips, the chair is too low. This rotates your pelvis backwards and flattens your lower back, which is the position most people describe as “sinking into” a soft chair. It is also why a sofa is a terrible place to work.

Test 3: shoulders (armrest height)

Sit normally with your hands where they would be on a keyboard. Now let your shoulders drop.

Did they drop? If your shoulders were being held up by the armrests, they are too high. If your shoulders slumped down and your forearms lost contact, they are too low, and your shoulder muscles have been holding your arms up all day without you noticing.

Correct is: shoulders relaxed and level, elbows at roughly a right angle, forearms lightly supported.

This test surprises people because unsupported arms produce pain in the neck and upper shoulders, not in the arms. A large share of what gets blamed on a bad backrest is actually arm support, and it often pairs with a monitor at the wrong height — same region, same complaint, two different causes stacking up.

What you can ignore

• The headrest. It does nothing unless you are reclining. If you are reclining while working, your screen is in the wrong place.
• Lumbar “support” as a selling point. A fixed lumbar bulge positioned wrong for your spine is worse than none. Adjustable height lumbar is worth something. A moulded lump is marketing.
• Mesh versus foam. Preference, not ergonomics. Mesh runs cooler; good foam lasts better than cheap mesh.
• Anything with “gaming” in the name. Bucket seats are shaped to hold a body in one position, which is the opposite of what you want for eight hours.

If your chair fails

Fix what you can adjust first — you would be amazed how many chairs have levers their owner has never touched. Look under the seat, on both sides.

If it fails the two-finger test and has no seat-slide, that is a genuine reason to replace it, and seat-depth adjustment is the feature to refuse to compromise on.

But do the tests before you shop, not after. Walking into a purchase knowing “I need a seat depth that suits a shorter femur, and armrests that go low” is a completely different exercise from reading a list of the same eight chairs everyone recommends.

Why we are not recommending a chair yet

We went looking for one. We went through Amazon’s best-selling office chairs to find the highest volume seller that adjusts seat depth, and we could not find one.

The best-seller list is almost entirely chairs between about $30 and $90 — mesh task chairs, padded executive chairs, chairs with massage motors and footrests bolted on. None of them adjust seat depth, because a seat slide costs money and a headrest photographs better.

Meanwhile the chairs that do advertise adjustable seat depth are almost all recent listings with double-digit review counts. No track record, no long-run owner reports, nothing to tell you whether the mechanism still works in two years.

Even the strongest-selling mid-range ergonomic chair we checked — the Sihoo M57, around 8,000 ratings and one of Amazon’s own picks — adjusts headrest, lumbar height and depth, recline and seat height, but not seat depth.

So the honest position is: we have nothing to sell you here. When a chair with real adjustment and a real track record shows up, we will write it up. Recommending a chair that fails the first test on this page, because it happens to sell well, would make every other page on this site worthless.

In the meantime, get the free adjustments right — and if you do shop, take the three tests above into the shop with you.

The thing that beats all of it

No chair position is good for eight hours, including the correct one. The best-fitting chair in the world still holds you in one shape, and held shape is its own problem.

Get up every half hour. It does more than any purchase on this site, and it is free — which is exactly why you will not find it advertised.