How we calculate these numbers
Every number on this site — desk height, chair height, monitor height, standing desk height — comes from one model: four ratios of your stature, derived from published body-measurement data. This page shows where the ratios come from, how well they hold up against measured data, and where they stop working.
We publish this because “put your monitor at eye level” is not actionable until it becomes a number, and a number is not trustworthy until you can see how it was produced. If you disagree with something here, the underlying data is public and you can check it yourself.
The four numbers
| Target | Ratio | Why that height |
|---|---|---|
| Chair seat | 0.25 × height | Matches your popliteal height — floor to the underside of the thigh just behind the knee. Lower and your knees rise above your hips; higher and the seat edge presses into the thigh and cuts circulation. |
| Desk top | 0.40 × height | Your sitting elbow height measured from the floor. Elbows at roughly 90°, shoulders relaxed, wrists straight — that is the posture that does not load the trapezius all day. |
| Seated eye height | 0.70 × height | Where your eyes sit once you are in the chair. The top of the screen goes here, not the middle, so the neck stays neutral for the 95% of the time you are looking at the upper half of the page. |
| Standing desk | 0.63 × height | Your standing elbow height. Different coefficient from the sitting desk on purpose — a standing surface is ~23 cm higher than the one you sit at. |
Where the ratios come from
None of them are invented. Each is a body measurement divided by stature, taken from population data:
- Chair = popliteal height ÷ stature
- Desk = (popliteal height + sitting elbow height) ÷ stature
- Seated eye = (popliteal height + sitting eye height) ÷ stature
- Standing desk = standing elbow height ÷ stature
The unit trap. Sitting elbow height and sitting eye height are conventionally published as above the seat surface, while popliteal height and standing elbow height are published from the floor. Add the wrong pair and you get a monitor centre below the desktop — a mistake this site actually shipped once, listed under corrections below. Every number here is stated from the floor.
Cross-check against published data
The four ratios above were not fitted to the data below — they predate it on this site. So this is a genuine out-of-sample check: take measured population averages, derive the same ratios independently, and see how far apart they land.
| Target | Our ratio | Derived (male) | Derived (female) | Derived (mean) | At 175 cm | Difference |
|---|---|---|---|---|---|---|
| Chair seat | 0.25 | 0.253 | 0.248 | 0.251 | 43.8 cm vs 43.9 cm | 1 mm |
| Desk top | 0.40 | 0.394 | 0.394 | 0.394 | 70.0 cm vs 69.0 cm | 10 mm |
| Seated eye height | 0.70 | 0.707 | 0.708 | 0.708 | 122.5 cm vs 123.8 cm | 13 mm |
| Standing desk | 0.63 | 0.626 | 0.624 | 0.625 | 110.2 cm vs 109.4 cm | 8 mm |
The largest gap is 13 mm, on seated eye height. That matters less than it looks: it is one fifth of the individual variation in the same measurement, and roughly one notch on a monitor arm.
We later ran a second, harder check: not against population averages but against individual-level records for 6,068 adults in the ANSUR II survey, computing each person's own sitting elbow height and comparing it to their own stature. That test is stricter — it looks at the median of a distribution rather than the mean of a mean — and the desk coefficient came out at 0.3832, about 29 mm below the 0.40 we publish. Chair came out at 0.2428 (13 mm below), seated eye height at 0.7016 (3 mm above). Full analysis, data and script.
We kept the round coefficients rather than switching to the derived ones. A 10 mm difference is below the adjustment resolution of most gas-lift chairs, and a memorable rule you can apply without a calculator is worth more than 1 cm of nominal precision.
Why the calculator only asks for height
Because the ratios barely move between sexes. Same data, same four divisions:
| Ratio | Male | Female | Gap |
|---|---|---|---|
| Seat height | 25.29% | 24.84% | 0.44 pp |
| Desk height | 39.37% | 39.44% | 0.07 pp |
| Seated eye height | 70.69% | 70.81% | 0.12 pp |
| Standing desk height | 62.64% | 62.42% | 0.22 pp |
Every gap is under half a percentage point — under 9 mm at 175 cm. A gender field would add a form input and buy approximately nothing, so there isn't one.
Why these are starting points, not answers
Population averages describe a population, not you. These are the standard deviations in the same dataset (mm):
| Measurement | SD (male) | SD (female) | 95% of people fall within |
|---|---|---|---|
| Popliteal height → chair | 29 mm | 27 mm | ±55 mm |
| Sitting elbow height → desk | 31 mm | 29 mm | ±59 mm |
| Sitting eye height → monitor | 35 mm | 33 mm | ±67 mm |
| Standing elbow height → standing desk | 52 mm | 46 mm | ±96 mm |
Read that last column again. Two people of identical height can differ by ±6 cm in sitting elbow height and still both be perfectly ordinary. Long torso and short legs, long legs and short torso — same stature, very different desk.
So the calculator gives you the number to start from, and three checks tell you whether to move off it:
- Elbows at 90° with shoulders relaxed — if you are shrugging, the desk is high; if you are reaching down, it is low.
- Feet flat on the floor — if they are not, the chair is too high for you and you need a footrest, not a taller desk.
- Eyes level with the top of the screen — if your chin tilts up, the screen is too high.
Where the calculated number and your body disagree, your body wins. The numbers get you to the right 5 cm; the checks settle the last 2.
Where this breaks down
- The source data is old and narrow. It describes British adults aged 19–65 measured in the mid-1980s. Populations have shifted, and this is not a global sample. Treat the ratios as a reasonable approximation for adults, not as a measurement of you.
- Linear scaling fails at the extremes. The ratios are fitted across roughly 150–195 cm. Below 150 cm and above 200 cm the error grows, because limbs and torso do not scale proportionally with stature. At the extremes, measure yourself instead: sit against a wall, bend your elbow to 90°, and measure floor to elbow.
- Not for children or adolescents. Body proportions change through growth; adult ratios do not transfer.
- Not for wheelchair users, or for anyone whose seated posture is constrained by equipment, injury, or a condition that affects posture. The model assumes an unconstrained seated position.
- This is not medical advice. Setup geometry can reduce mechanical strain; it does not diagnose or treat anything. Persistent pain, numbness, or weakness belongs with a clinician or a physical therapist, not a calculator.
Sources
We did not run our own survey. Everything above is derived from:
- Pheasant, S. (1986), Bodyspace: Anthropometry, Ergonomics and the Design of Work. Adult British population aged 19–65. The summary table is reproduced in open course material from The Open University.
- Gordon, C.C. et al. (2014), 2012 Anthropometric Survey of U.S. Army Personnel: Methods and Summary Statistics, NATICK/TR-15/007. Public release: 4,082 male and 1,986 female subjects, 93 direct measurements. Available via Penn State OpenLab. We cite it as an independently checkable dataset, not as the source of the coefficients above.
Both are free to access. If you want to re-derive the numbers — please do. Corrections are welcome at hello@yangmk.com, especially if you include what you actually measured.
Corrections
Published mistakes, kept on the record. A site that quietly edits its errors is not the same as a site that shows them.
| Date | What was wrong | What changed |
|---|---|---|
| 2026-09-16 | Standing desk height was published as 40% of stature — the same coefficient as a sitting desk, which is obviously wrong once you stand up. | Corrected to 63%. For a 170 cm person that moved the target from 68 cm to 107 cm. Affected: the standing desk guide. |
| 2026-09-16 | Seated eye height was written as if measured from the seat surface, while desk and chair heights were measured from the floor. Mixed units produced screen centres below the desktop. | All four targets are now stated from the floor, and every height page says so explicitly. Affected: eight height pages. |
Who writes this
yangmk is written by yangmk — an engineer who measures his own setups instead of guessing at them.. One person, no editorial team, no medical credentials: the value here is arithmetic you can check, not authority you have to take on faith.
More about why the site exists on the about page.
Where to go next
- Is standard desk height too tall? — the same model tested against 6,068 individually measured adults, not averages
- Desk height calculator — get your four numbers
- Complete ergonomic desk setup guide — the order to change things in, which matters as much as the numbers
- Workspace checkup — score the desk you already have