How we do the maths
We would rather show the method than ask you to trust us.
The principle
The workstation adapts to the body. Seat height starts from popliteal height; work surface height from elbow height; screen height from eye height. These are classic principles of applied anthropometry (Pheasant & Haslegrave, 2006) and of ISO 9241-5:2024.
The sums
- Seat = popliteal height + 2.5 cm for shoes
- Surface (seated) = seat + elbow height above the seat
- Top of screen ≤ seat + seated eye height
- Standing bench = standing elbow height + shoes, plus or minus a range that depends on the task (precision above, force below)
- Difference: up to 5 cm fitted; 5–10 cm to adjust; over 10 cm far off
What is our own convention
The shoe allowance, clearances and the 5 and 10 cm thresholds are internal conventions, declared as such. They are not values from a standard. The exposure level in the self-assessment is a classification rule that has not yet been validated.
Measured or estimated
When we only have your height, we estimate the other measurements by proportion and show the margin of error. The current ratios are provisional and will be replaced by population data.
What standards do and do not do
EN 527-1:2011 (desks) and EN 1335-1:2020+A1:2022 (chairs) define furniture dimensions and adjustment ranges. They do not calculate the ideal height for a person, and they do not certify software. We use them to say whether a piece of furniture covers your measurements.
Observational methods
Methods such as RULA, REBA and the NIOSH equation require a trained observer. We do not apply them in self-assessment.
Limits
- Self-assessment, not a formal risk assessment
- Does not diagnose, treat or predict disease
- Self-taken measurements carry error, which is why we show margins
- We do not yet have an agreement study against on-site assessment: it is planned
Main references
- ISO 9241-5:2024. Ergonomics of human-system interaction — Part 5: Workstation layout and postural requirements.
- ISO 7250-1:2017. Basic human body measurements for technological design — Part 1.
- EN 527-1:2011. Office furniture — Work tables and desks — Part 1: Dimensions.
- EN 1335-1:2020+A1:2022. Office furniture — Office work chair — Part 1: Dimensions.
- Pheasant, S., & Haslegrave, C. M. (2006). Bodyspace (3rd ed.). CRC Press.
- Barroso, M. P., Arezes, P. M., da Costa, L. G., & Miguel, A. S. (2005). Anthropometric study of Portuguese workers. International Journal of Industrial Ergonomics, 35(5), 401–410.
- Waters, T. R., Putz-Anderson, V., Garg, A., & Fine, L. J. (1993). Revised NIOSH equation. Ergonomics, 36(7), 749–776.
- McAtamney, L., & Corlett, E. N. (1993). RULA. Applied Ergonomics, 24(2), 91–99.