Desk setup calculator

Set the chair before you touch anything else

The chair is the reference point for everything above it, so a desk measured from the wrong seat height is wrong twice. Sit back fully, put your feet flat, and adjust until your thighs are roughly level and there is no pressure at the back of your knees. If your feet dangle, the seat is too high; if your knees are noticeably above your hips, it is too low.

Then check the desk against your forearms rather than against the tape. Sitting as above, your forearms should come level with the surface without shrugging your shoulders or dropping your wrists. Most fixed desks sit between 72 and 75 centimetres, which is slightly too high for anyone under about 180 centimetres — and that is the single most common problem in a home setup.

When the desk will not move

A fixed desk that is too high has one good fix and one bad one. The bad fix is to raise the chair and let your feet dangle, which transfers the problem to your lower back. The good one is to raise the chair until your forearms are level and then support your feet — a footrest, a box, a stack of books, anything solid enough that your thighs stay level.

A desk that is too low is harder, because a chair can only go so far down before your knees are in the way. Raising the desk on sturdy blocks under the legs is usually easier than replacing it, and it also fixes the standing case if you switch to a converter later.

• Too high, with an adjustable chair: raise the chair to forearm level and add a footrest.
• Too high, with a fixed chair: a thicker seat cushion buys a few centimetres.
• Too low: raise the desk itself; sitting lower to reach it puts the strain in the shoulders.
• Keyboard and mouse on the same level, close enough that your elbows stay near your sides.

The screen, and why a laptop cannot win

The target for a separate monitor is straightforward: the top edge at or just below eye level so your gaze drops a few degrees, and about an arm’s length away — 50 to 70 centimetres is a fair range, further if the text is still comfortable. Looking slightly down is easier on the eyes and neck than looking up, and it also exposes less of the eye surface, which matters if your eyes dry out by the afternoon.

A laptop cannot satisfy both requirements at once, because the screen and keyboard are joined. Raise the screen to eye height and the keyboard rises with it, so your shoulders lift; leave the keyboard at desk height and you spend the day looking down. There is no clever posture that resolves this — the fix is a stand plus a separate keyboard and mouse, which is the cheapest ergonomic upgrade there is.

If a stand is not an option, the working compromise is the laptop flat and the desk at the seated height, accepting the downward gaze, and raising the screen for long stretches of reading where you are not typing.

A standing desk is a second position, not a better one

Standing all day is not an improvement on sitting all day; it just moves the load to your feet, knees and lower back. The benefit of a height-adjustable desk is that it lets you change position, and changing position is the part that helps.

For the standing height, the same forearm rule applies: elbows at about a right angle with your shoulders relaxed, standing tall without leaning on the desk. That is roughly 60 per cent of your height, which is 105 centimetres for someone of 175. Start with an hour or so of standing spread across the day rather than a heroic first afternoon, and put something soft underfoot if you are on a hard floor.

The number that matters more than any of these

No arrangement of furniture is comfortable for eight unbroken hours, and a perfectly measured setup held rigidly still is worse than an imperfect one you move around in. Regular breaks — standing up, walking a few steps, looking at something far away — do more for how you feel at 5 pm than the last centimetre of monitor height.

For eyes specifically, the widely repeated habit is to look at something around 20 feet away for about 20 seconds every 20 minutes. The evidence for the exact intervals is thin, but the principle is sound: eyes fixed at one distance for hours are the problem, and periodically changing the distance is the fix.

My desk is 75 centimetres and the calculator says 70. Do I need a new desk?

No. Raise your chair until your forearms are level with the desk, then support your feet so your thighs stay level. That reproduces the same geometry with the furniture you already own.

Should the top of the monitor be at eye level or below it?

At eye level or a few centimetres below, so your gaze drops slightly when you look at the middle of the screen. Higher than eye level tips your head back, which is the position that tires the neck fastest.

Does it change anything if I use two monitors?

The heights stay the same. Put the one you use most directly in front of you and angle the second one in beside it — a symmetrical pair with the gap in the middle means you spend the day turned slightly to one side.

How long should I stand at a standing desk?

There is no established figure. Alternating is what matters, so start with short spells adding up to about an hour a day, spread out, and increase only if it feels better rather than because a number says so.

Is a kneeling chair or a balance ball better than a normal chair?

Neither has convincingly beaten a well-adjusted conventional chair, and both make it harder to get the forearm and screen geometry right. Get the ordinary setup correct first; that is where the available gain actually is.