What Height Should Your Chair Be?

Most chair advice tells you to set your seat so your feet are flat on the floor. That is half right, and the missing half is what causes most of the trouble: your chair height is not a property of your chair, it is a consequence of your desk height.

Set the chair to your body and the desk ignores you. Set the chair to the desk and your body pays for it. The order that works is desk first, chair second, and then — only if the two refuse to meet — a footrest.

The number: 25% of your height

Your seat height should land close to your popliteal height, which is the distance from the floor to the underside of your thigh just behind the knee. Across adult populations that works out to roughly 25% of standing height:

That is the target, not the instruction. What you actually dial in depends on the desk in front of you.

(Measured rather than averaged — 6,068 adults, individual records — the median is 24.3% of height, about 13 mm below the round 25%. Full distribution here.)

The order that actually works

Step 1 — find your desk's working height. If you have not measured it yet, the desk height calculator gives you your seated elbow height, which is what the desk surface should match. For most people that is around 40% of height — about 70 cm at 175 cm.

Step 2 — set the chair so your elbows land on it. Sit back, let your shoulders drop, and bend your elbows to 90°. Adjust the seat until your forearms rest on the desktop without your shoulders rising. Shoulders creeping up toward your ears is the tell that the chair is too low; elbows flaring out and wrists bending up is the tell that it is too high.

Step 3 — check your feet, and only now worry about them. If your feet rest flat, you are done. If they dangle, you need a footrest — and the thickness you need is exactly the gap you just measured. If your knees end up higher than your hips, the chair is too low and no footrest will save it.

The reason this order matters: a chair set from the floor upward assumes your desk is the right height. In an office with fixed 29-inch desks, it usually is not.

Why the standard advice fails short people

A fixed 29-inch (73.5 cm) desk and a 5'2" (157 cm) person do not fit. To get their elbows up to that surface, they have to raise the seat to roughly 46 cm — but their popliteal height is around 39 cm. Raise the chair by 7 cm and the feet come off the floor.

This is the single most common setup failure, and the fix is never "buy a better chair." It is one of:

• A footrest — bridges the gap. Needs to be thick enough to actually take weight, not a decorative 2 cm wedge.
• A keyboard tray — drops the working surface instead of raising the person. Usually the better fix, because it also preserves the desk's standing height.
• An adjustable frame — the only option that fixes sitting and standing at once.

If you are under about 5'4", read the full desk height guide for short people — the chair is only one of three numbers involved.

Why it fails tall people too

At 6'4" the problem inverts. Standard desks bottom out around 27–29 inches and the seat goes down to fit, but then the knee angle closes past 90° and the hips roll backward, flattening the lumbar curve. Tall people often compensate by sliding forward onto the front edge of the seat, which removes the backrest from the equation entirely.

The tell is easy to spot: if you are tall and your lower back hurts by mid-afternoon, look at where your pelvis actually is. Sitting on the front third of the seat is not a chair height problem, it is a seat depth problem that begins as a chair height problem.

The three checks that confirm it

Once you think you are set, run these:

1. Two-finger test — slide your fingers under your thigh at the front edge of the seat. If you cannot, the seat is pressing into the back of your knee and it is too high.
2. Knee angle — your knees should sit at or slightly below hip level. Hips lower than knees means the seat is too low relative to the desk.
3. Shoulder check — after a minute of typing, are your shoulders still down? If they have crept upward, the surface is too high for that chair, and lowering the chair 1 cm will feel wrong but type better.

If you want all three numbers checked against each other rather than one at a time, the workspace checkup scores desk, chair, and screen together and tells you which single adjustment fixes the most.

FAQ

Should my feet be flat on the floor?

Ideally yes, but not at the cost of your elbows. If flat feet and relaxed shoulders cannot both happen, keep the shoulders and add a footrest. Dangling feet are only a problem because they make you slide forward — a footrest removes that.

My chair will not go low enough. What now?

Your desk is too low, not your chair. Do not raise the chair and reach upward. Raise the desk with risers or bed risers under the legs (cheap, ugly, effective), or get an adjustable frame. Reaching up to type is worse than any other compromise on this list.

How much does seat height actually matter?

Less than desk height and less than screen height, which is why the workspace checkup weights it at 20% against 35% for the desk and 45% for the screen. But it is the number that decides whether the other two are reachable at all.

Is a kneeling chair or a saddle stool better?

They solve a different problem. Kneeling chairs rotate the pelvis forward, which helps people who cannot stop slumping — but they shift load onto the knees and shins, so they are a part-time option, not an eight-hour one. Saddle stools open the hip angle and work well at a higher desk, which makes them a reasonable match for a standing desk used sitting.

Related

• Ergonomic desk setup: the complete guide — where chair height sits in the five-number sequence.
• What height should your monitor be? — once the chair is right, the screen number changes with it.
• What height should your keyboard and mouse be? — the third number in the same chain.
• How to sit at a desk correctly — chair height gets you in range; posture decides whether you stay there.
• My chair won't go low enough — when the seat bottoms out above your popliteal height and a footrest is not the answer.
• My desk is too high and I can't adjust it — the case where raising the chair is the wrong move.
• How to set up a standing desk — the standing number is a different calculation entirely.