How to adjust your chair

Almost everyone adjusts a chair in the wrong order, and the wrong order is not a small inefficiency — it means some of the adjustments you make get undone by the next ones. Most people start with the backrest, because it is the part you can see. The backrest is step four.

Here is the sequence, and the reasoning underneath each step. It takes about ten minutes and costs nothing, which makes it the best value on this entire site.

Step 0: your desk decides, not your body

This is the step that gets skipped, and skipping it is why so many people end up fighting a chair that was fine.

Your keyboard sits on your desk. Your desk, unless it is a sit-stand, does not move. So the height of your elbows is decided by the desk before you sit down — and the chair’s job is to deliver your elbows to that height. The chair is downstream. Adjusting a chair without knowing your desk height is aiming at nothing.

So: measure your desk, floor to the top of the surface. If it moves, set it first — the desk height calculator gives you a target. If it does not move, write the number down anyway, because it is about to explain everything else on this page.

Worth clearing one thing up while you are down there, since you will see it repeated everywhere: OSHA does not prescribe a desk height. Its Computer Workstations eTool contains posture principles and exactly one desk number — leg clearance of 20–28 in (50–72 cm) under the desktop. That is a clearance, not a work surface. Every “OSHA says your desk should be 29 inches” you have ever read was invented by whoever wrote it.

Step 1: seat height, set from the desk

Sit down and raise or lower the seat until your elbows are at roughly the height of the desk surface, with your upper arms hanging near vertical. That is it. Not your height, not a formula, not a number off a chart — your elbows, at your desk.

Now apply OSHA’s test, which is the only definition they give:

“The chair height is appropriate when the entire sole of the foot can rest on the floor with the back of the knee slightly higher than the seat of the chair.”

Read that carefully, because it is doing two jobs. The entire sole — not your toes. And the back of the knee slightly higher than the seat, which means the seat is not level with your knee, it is marginally below it. That is a fit test. There is no correct seat height in inches; there is only a correct seat height for you, at your desk.

And now, for most people, the two halves of this step are about to disagree.

The conflict — and why the answer is a footrest

Set your elbows to a conventional desk and there is a good chance your feet no longer touch the floor. This is not you doing it wrong. It is arithmetic, and it is worth seeing it laid out.

The ANSUR II anthropometric survey publishes median measurements for popliteal height (floor to the back of the knee) and seated elbow rest height. Add them together — barefoot, seat at popliteal height, elbow at 90° — and you get the height a work surface would need to be:

• Median male: 67.6 cm, about 26.6″
• Median female: 62.0 cm, about 24.4″

Both of those are our own arithmetic on ANSUR’s published percentiles, not a figure anybody published as a desk height — and ANSUR is a military population, younger and fitter than the people reading this. Treat them as an illustration of the direction, not as your number.

The direction is unambiguous, though: both sit well below the conventional fixed desk, which is around 29″. The median adult does not need a 29-inch desk. Nobody in that calculation does.

There is a sharper version of the same point in the standard. ANSI/HFES 100 — a genuine ANSI-accredited national standard, unlike most of what gets waved around in this category — requires that a sit-only input surface shall adjust over at least 56–72 cm (22–28.3″). Look at the top of that mandated span. It is 28.3″. The ordinary desk in your room is above the entire range the standard says an adjustable surface must be able to cover.

So when your elbows are at the desk and your feet are dangling, the chair is not the problem and the fix is not to lower the seat. Lower the seat and your elbows drop below the desk, and you spend the day with your shoulders raised to reach the keyboard — you have moved the compromise, not removed it.

Keep the elbows. Raise the floor. A footrest is what that means, and it is the unglamorous conclusion of the entire page: a solid box, a ream of paper, an actual footrest, anything that lets the whole sole rest flat with the back of the knee slightly higher than the seat. It is the cheapest fix on this website and it exists because the standard desk is the wrong height for most of the people using it.

(The other fix is a desk that comes down to you, which is why we bang on about floor height rather than top height in the desks roundup. Across that field the bottom of the range runs from 21.6″ to 29.2″ — and a desk whose floor is 29.2″ is, at its lowest setting, just a desk.)

Step 2: seat depth

Now slide fully back, so your backside is in the corner where the seat meets the backrest. Check the gap between the front edge of the seat and the back of your knee. You want a gap — roughly two to three fingers is the usual rule of thumb, and we would rather call it a rule of thumb than dress it up as a standard, because it is not one.

Why it matters more than it looks: if the pan is too deep, the front edge meets the back of your knee when you sit properly back, so you slide forward to escape it — and then your back is no longer touching the backrest. At which point the entire backrest, including whatever lumbar mechanism you paid for, is supporting nothing. It is the step that decides whether steps three and four exist at all.

If your chair has a seat-depth adjustment, this is where you use it. Many don’t — and most that do will not tell you the range before you buy. Steelcase publishes 2¼″ of travel on the Series 1; across our whole chairs roundup, that is the only published seat-depth figure. If yours has none and the pan is too deep, a cushion behind your back is a legitimate fix, because it does the same thing: it moves the effective back of the seat forward.

Step 3 & 4: backrest height, then lumbar

If the backrest height adjusts, set it so the curved part sits in the small of your back — the hollow you can feel with your hand when you stand up. Then set the lumbar depth, if you have that separately, so it makes contact without pushing you off the backrest.

The whole reason this is step four and not step one: a lumbar support is an object that fills the gap between your lower back and the backrest. That requires you to be at the backrest, which was decided by seat depth, which was decided by seat height, which was decided by your desk. Set it first and you have aimed a mechanism at a position you will not be sitting in. There is more on the geometry in what lumbar support actually does.

Step 5: recline and tension

OSHA’s chairs page says the backrest “should recline at least 15 degrees from the vertical”. So if you have been working bolt upright with the tilt locked, that is worth knowing: upright is not the target position, it is one end of the range.

Set the tilt tension for your weight — heavy enough that you do not fall backwards when you lean, light enough that you can actually rock without bracing. Then unlock it, if it locks. The point of a recline is to be used.

And note the interaction with step four: if you set the lumbar upright and then spend the day reclined, you set it for a posture you do not use. Recline first, then re-check the lumbar in the position you actually work in.

Step 6: armrests, and when to remove them

Armrests are last on the chair, and they are last because they are the only adjustment that is allowed to lose.

Set them so they meet your elbows where your elbows already are — you do not raise your shoulders to reach the armrests, they come up to you. If they will not go high enough, they are decoration. If they go too high and will not come down, they will push your shoulders up all day.

And here is the one that catches people: if the armrests stop you getting close enough to the desk, take them off.Remember OSHA’s one desk number — 20–28 in of leg clearance underneath. If your armrests are colliding with the desk edge, you are sitting further back than you should be and reaching for the keyboard, and every good thing you did in steps one through five is now being undone by the arms. A chair with no armrests, pulled properly under the desk, beats a chair with lovely 5D armrests parked six inches too far away.

Step 7: the monitor, now that you have moved

Only now. Everything above changed your eye height — possibly by several inches, and the recline changed it again. A screen set before the chair was set is a screen aimed at somebody else.

OSHA’s guidance: “The top of the monitor should be at or slightly below eye level”, the centre “15 to 20 degrees below horizontal eye level”, and a preferred viewing distance “between 20 and 40 inches (50 and 100 cm)”. Worth knowing that the popular “top of screen at eye level” rule is the weaker version of this, and that the research HFES 100 cites points lower still. We work through that, and the trade-off it involves, in the monitor height guide.

The short version

1. Measure the desk. It decides everything downstream.
2. Seat height until your elbows meet the desk.
3. Feet: whole sole flat, back of the knee slightly higher than the seat. If they dangle, raise the floor, do not lower the seat.
4. Seat depth: two or three fingers behind the knee.
5. Backrest and lumbar, into the hollow of your back.
6. Recline at least 15°, tension set to your weight, unlocked.
7. Armrests to your elbows — or off, if they fight the desk.
8. Monitor last.

Then leave it a week and do it again. You will have got something wrong, and the second pass is free. If after all that your chair still cannot deliver your elbows to your desk with your feet supported, the chair genuinely is the problem — and the number to shop on is the published seat-height range, which half the category will not tell you.