Which of the Five Numbers Is Wrong? A Symptom-to-Cause Chart

You set your desk up using a chart, and something still hurts. The usual response is to adjust everything a little — chair down, monitor up, cushion in — which makes it impossible to tell what helped, and often makes one thing better while another gets worse.

Pain at a desk is not random. Each of the five numbers produces a fairly distinct signature, so you can work backwards from where it hurts to which number is off. This page is the reverse lookup.

The five numbers, in the order they should be set: desk height, chair height, footrest, screen height, keyboard and mouse. Why that order matters is the single most useful thing on this site: ergonomic desk setup.

The chart

Read the row that matches, do only that test, and change only that number. If two rows apply, fix the one higher up this list first.

If you are not sure whether "desk too high" really applies to you — it usually does. In a sample of 6,068 adults whose elbow height was measured rather than estimated, 73% need a desk lower than 73 cm.

Neck and headaches: the screen, almost always

The most misdiagnosed complaint at a desk. The pain is in the neck, so people buy a chair, a cushion, or a new pillow. The cause is usually up at eye level.

When the screen sits below your eyes — far below, in the case of a laptop lying flat — your head tips forward to aim your eyes at it. Your head weighs around 5 kg, and holding it forward for hours loads the muscles at the back of the neck and the top of the shoulders continuously.

The number: the top edge of the screen sits level with your eyes, which is about 70% of your height from the floor when seated. For a 175 cm person that is roughly 123 cm. A 27" monitor's centre then lands about 17 cm below its top edge.

Quick check: put the screen on a stack of books so the top edge reaches your eyes and sit for twenty minutes. If the ache eases, you never had a chair problem. Full detail in what height your monitor should be, and if you are on a laptop, laptop ergonomics and neck pain.

Shoulders: the desk is too high

A band of tension across the top of the shoulders, sometimes into the neck, usually means your arms are being held up rather than supported. When the work surface is above your elbows, the trapezius does the holding — continuously, for hours, which is exactly what that muscle is bad at.

The number: the keyboard surface should be at or 1–2 cm below your seated elbow height, which is near 40% of your height. Add 2–3 cm if you type on a keyboard resting directly on the desk.

The trap: the standard response is raising the chair, which brings your elbows up to the desk and leaves your feet dangling. You have moved the problem to your legs and your lower back. If the desk cannot be lowered, the fixes are in my desk is too high and I can't adjust it.

Wrists and forearms: height, then distance

Two separate causes with the same symptom.

Wrist extension — the back of your hand bent upward while typing — comes from a keyboard that is too high or a desk that is too thick for you. It is the same number as the shoulder problem, felt further down the arm.

Reaching comes from a mouse that sits too far away, or a keyboard pushed back so you type with your arms extended. The mouse should be directly beside the keyboard, close enough that you are not reaching forward, and both should be roughly at elbow height.

Full detail in keyboard and mouse height. Note that wrist rests treat the symptom and can make the reaching worse by pushing your hands further from the keys — fix the height first.

Lower back: three different causes

Lower back pain does not have one cause, which is why lumbar cushions help some people and do nothing for others. The three:

1. Seat too high — the pelvis rotates backward under thigh pressure and the lumbar curve flattens. You slide forward; your back is stiff when you stand.
2. Seat too deep — you cannot reach the backrest, so your lower back holds your torso up unaided.
3. Lumbar support in the wrong place — a cushion behind your mid-back instead of the inward curve does nothing.

That is a page of its own: desk setup for lower back pain. One useful screening test first: raise the screen and sit for twenty minutes. If the back pain goes, the cause was up at eye level all along.

Legs and feet: the seat is too high

Numbness, tingling, or calves that fall asleep point at pressure behind the knees from a seat that is too high, or at having no floor under your feet at all.

The number: seat height should be close to your popliteal height, around 25% of your height. If your chair bottoms out above that, it is a different fix from "add a footrest" — see my chair won't go low enough.

Fix them in this order, or you will fix them twice

The five numbers are not independent. Change one and the others move:

• Lower the desk → the chair may now be too high, and the screen is too high.
• Raise the chair → your eyes rise, so the screen does too, and your feet leave the floor.
• Raise the screen → nothing else changes, which is why screen height is usually the right first move.

The order that avoids rework: desk → chair → footrest (only if needed) → screen → keyboard. Desks are the hardest thing to change, so they get decided first and everything else adapts to them.

If you have been adjusting for weeks without getting comfortable, it is usually because you fixed number four while number one was still wrong.

When it is not the setup

Some patterns are not furniture problems, and no amount of adjustment will fix them:

• Numbness or tingling that persists after the seat is right, or pain that radiates down a leg or into the hand.
• Pain that is there in the morning before you sit down, or that wakes you at night.
• No change at all after two weeks of a correctly set up workstation.
• One-sided weakness, or pain following an injury.

These are worth a clinician's opinion. This page is about the numbers on a desk, not diagnosis.

FAQ

I fixed everything and it still hurts. What now?

Check whether you fixed them in order. Most people adjust the chair and the monitor while the desk is still wrong, and the desk quietly undoes the rest. Start again at the desk. If nothing changes after two weeks of a genuinely correct setup, the cause is probably not here.

Which single change fixes the most?

Usually screen height. It is the cheapest, it is independent of the other numbers, and it is the cause most often missed because the pain shows up somewhere else.

Why does it hurt in one place and come from another?

Because load travels. A low screen pulls your head forward, which pulls your shoulders forward, which flattens your lower back. The pain is at the end of the chain; the cause is at the start.

Should I buy a new chair?

Only after the desk and the screen are right. Most "my chair is bad" reports turn out to be a desk that is too high for the person, which a new chair cannot fix. Once the desk is correct, if your chair still cannot reach the right height, that is when it is a chair problem.

How long before it feels better?

Positional pain usually eases within a few days of correcting the number that is wrong, and within two weeks if it has been going on for months. No change at all after two weeks means the cause is elsewhere.

Related

• Ergonomic desk setup: the complete guide — the five numbers in order, plus the cascade that explains why order matters.
• Desk setup for lower back pain — the lower back row in detail.
• What height should your monitor be? — the neck row in detail.
• My desk is too high and I can't adjust it — when the surface cannot be moved.
• My chair won't go low enough — when the seat bottoms out.
• Workspace checkup — enter your measurements and see which single change scores the biggest improvement.