How to sit properly at a desk

There is a companion page to this one about the chair’s levers — how to adjust your chair, which knob to turn and in what order. This page is about something different: the shape you are turning them to reach. The posture itself. The set of joint angles that a chair, a desk and a screen are all, in the end, just trying to deliver your body into.

And the useful way to describe that shape is from the floor up, because that is how a seated body stacks. Your feet decide where your knees can be. Your knees and hips decide where your back sits. Your back decides where your shoulders hang. Your shoulders decide where your forearms land. And only once all of that is settled does it make any sense to talk about your head and the screen it is pointed at. Get the order backwards — set the monitor first, then adjust everything under it — and the top of the stack ends up fighting the bottom.

So we have taken OSHA’s Good Working Positions, its description of a neutral seated posture, and walked it upward one joint at a time. Every quoted line below is OSHA’s; the reasoning between the quotes is ours; and there is one closing idea, from Cornell’s ergonomics group, that quietly undoes the whole premise of a single “correct” posture. We have saved it for the end because it reframes everything before it.

Start at the floor: feet flat, or a footrest

The first thing OSHA’s neutral posture asks for is the least glamorous: the feet are flat on the floor or a footrest. The whole sole, planted — not the toes, not the balls of the feet, not a heel hooked on a chair caster.

This is genuinely the foundation and not a figure of speech. A foot that is planted gives the leg something to push against and lets the weight of the leg rest on the floor instead of hanging off the front edge of the seat. A foot that dangles does the opposite: it loads the underside of the thigh against the seat pan, and it leaves the joints above it with nothing stable to be arranged on top of. You cannot sensibly set a knee angle, a hip angle or a back angle on a base that is swinging in the air.

Here is the catch that OSHA has already anticipated by writing “or a footrest.”A conventional fixed desk is tall — tall enough that when you raise the seat until your elbows meet it, a lot of people’s feet come off the ground. That is not you sitting wrong; it is the desk being higher than your body needs, which is the arithmetic we work through on the desk height calculator. The answer is not to drop the seat — that pulls your elbows down below the desk and trades a foot problem for a shoulder one — but to raise the floor to meet your feet. A solid box, a ream of paper or an actual footrest all do the same job. Whichever you use, the target is the same: the whole sole supported, so everything above it has a base.

The thighs and hips: parallel, and a little open

With the feet planted, look at the thighs. OSHA describes them as roughly parallel to the floor, with the knees about level with the hips. That is the second block in the stack, and it follows directly from the first: if the feet are flat and the thighs are level, the knee lands at somewhere near a right angle almost by itself.

The hip is where the popular “sit at 90 degrees” instruction is slightly, usefully wrong. A rigid right angle at the hip is a cramped position to hold. In practice the hip sits a little more open than that — the thighs angling very gently down from the hip rather than dead level — which keeps the joint from being pinned shut. We are describing that as geometry, not quoting it as a number, because OSHA does not publish a hip-angle figure and we are not going to invent the precision of one. The principle is the safe part: the hip wants to be open, not clamped, and the thigh wants to be near-parallel to the floor rather than sloping sharply either way.

The other thing this block decides is contact with the backrest, and that is really a chair-fit question rather than a posture one. If the seat pan is too deep, its front edge meets the back of your knee before your spine reaches the backrest, so you slide forward to escape it — and now your back is off the backrest entirely, which quietly cancels the next step before you get to it. That is exactly the kind of thing the chair-adjustment sequence exists to sort out. For posture, the thing to know is that the hips need to be all the way back in the seat for anything above them to work.

The lower back: supported, and leaning back a little

Now the spine. The instinct, drilled into most of us, is to sit up straight — bolt upright, chest out, as if good posture were a matter of rigid verticality. OSHA’s own chairs guidance says otherwise. The backrest “should recline at least 15 degrees from the vertical.”

Read that carefully, because it inverts the usual picture. Upright is not the destination; it is one end of a range, and the neutral position sits a little behind it, leaning back. The job of the backrest is to take some of the load that your lower back would otherwise carry on its own, and it can only do that if your back is actually against it — which is why the seat-depth point above matters, and why a lumbar support set for someone sitting bolt upright does nothing for someone who spends the day reclined.

So the third block in the stack is: hips all the way back, lower back in contact with the backrest, and the whole assembly tipped back at least a little rather than held at a strained vertical. If you have been working rigidly upright with the tilt locked, this is the line worth taking away — the recline is not slouching, it is the position OSHA describes as neutral.

The shoulders and forearms: relaxed, level, neutral

Up one more level to the shoulders and arms, and here the reference shifts from OSHA’s chairs and positions pages to its keyboards page, because this is where the body meets the desk.

The shoulders come first, and the instruction is simply that they are relaxed — hanging, not hitched up toward the ears. A shrugged shoulder is usually a symptom of something set wrong lower down or off to the side: a desk that is too high, or armrests parked too tall, forcing you to lift to reach. OSHA’s chairs guidance is that armrests should support the forearms without making you shrug; if yours push your shoulders up, they are working against you and are better lowered or removed.

With the shoulders down, the forearms set the desk relationship. OSHA’s line is precise: “Elbows should be about the same height as the keyboard and hang comfortably to the side of the body.”That is the single most load-bearing sentence for how high your work surface should be relative to you — the elbow, not the wrist and not the shoulder, is the thing you match to the keyboard. From there the forearms run roughly level to the keys, and the wrists stay straight and neutral rather than cocked up, down or off to a side. We give the wrist and forearm geometry its own full treatment on wrist and keyboard position, because it is where a surprising amount of desk discomfort is decided and it deserves more than a line.

Notice how much of this block was actually settled two steps ago. Whether your elbows can be level with the keyboard with your shoulders relaxed depends entirely on the height of the seat, which depended on the desk. That is the floor-up logic paying off: by the time you reach the arms, most of the work has already been done underneath them.

The head and the screen: balanced, at or below eye level

Last comes the head, and the screen it looks at — last on purpose, because every single step below it just moved your eye height, possibly by several inches, and the recline moved it again. A monitor set before the body is set is a screen aimed at a person who is no longer sitting there.

OSHA’s positions page asks for the head balanced over the spine — level and roughly in line with the torso, not craned forward or tipped down. The way you get there is not by holding your neck in place; it is by putting the screen where a balanced head naturally looks. OSHA’s monitors page gives the geometry for that in three numbers: “the top of the monitor should be at or slightly below eye level,” the center of the screen “15 to 20 degrees below horizontal eye level,” and a “preferred viewing distance… between 20 and 40 inches.”

Put plainly: the top of the panel sits at about your eye line or a touch under it, your gaze falls gently rather than climbing, and the screen is roughly an arm’s length away — anywhere in that 20-to-40-inch band. If the top of your screen is above your eyes you will tip your head back to read it; if it is far too low you will drop your chin to it. The balanced head is the one that does neither, and the screen’s job is to make that the comfortable place to look. The full walk-through, including the trade-offs the number hides, is in the monitor height guide.

The step that undoes all of it: the best posture is the next one

Here is the idea we held back, and it is the most important thing on the page. Everything above describes a single neutral position — and no single position, however neutral, is meant to be held all day.

Cornell’s ergonomics group frames the goal not as achieving one perfect posture but as changing position often — moving between positions rather than freezing in any of them, including a “correct” one. A textbook-neutral posture held rigidly for eight hours is still eight hours of one posture, and stillness is its own problem that no joint angle solves. The body is built to move; a chair, even a good one in a good position, quietly asks it not to.

This is why the phrase worth remembering is that the best posture is the nextone. The neutral shape assembled on this page is not a pose to lock into; it is a home base — the position that is safe to keep coming back to, precisely because you keep leaving it. Shift in the seat. Recline further, then come forward. Stand up. If you have a sit-stand desk, use both halves of it. The most useful thing you can do with the posture described above is get into it, and then, a while later, stop being in it.

That reframes the whole exercise in a way we think is honest. The point of learning the neutral posture is not to hold it. It is to have a good place to return to, so that all the moving around you do between returns starts and ends somewhere sound.

What this page is not

This is a description of geometry, not medical advice, and it is not written by anyone qualified to give any. Stephen is an enthusiast who reads standards documents and spec sheets — not a physiotherapist, not an ergonomist, not a clinician. What this page does is report how OSHA describes a neutral seated posture, quote it directly, link it, and walk it in the order a body stacks up. What it deliberately does not do is diagnose you, promise that any position will relieve or prevent anything, or imply a credential none of us hold. Positions are not treatments.

And even within the geometry, the sources are honest about their own limits. OSHA gives a fit test and a set of relationships, not a table of exact angles for your body, because the right numbers are yours and depend on your measurements and your desk. So take the floor-up sequence as the shape to aim for and a baseline to return to — then, per Cornell, keep leaving it. If something hurts and keeps hurting, the person to see has a license and can check things about you that no posture diagram can, and that is a better use of your time than a website with affiliate links on it.