Glossary
Peak
Planning on the average guarantees a shortage one day a week.
The peak is, in Workplaced's definition, the busiest realistic level of use in a measured period, expressed as a high percentile of the observed moments rather than the single highest reading. The measurement interval and the measure belong with the figure, because one all-hands day should not size a building and an average day should not either.
Also called Peak occupancy, Design day
How it is calculated
Peak = the nth percentile of observed occupancy across the measured period
- n
- The percentile chosen as the design point. P95 accepts a shortage on roughly one day in twenty; P90 on one in ten.
- Observed occupancy
- Every measured moment in the period, not the daily averages.
Expressed as A percentage, with the percentile stated alongside it.
This is a Workplaced definition, not a universal industry norm. Measurement interval: the time interval in which one observation is recorded, stated with the figure. Measure: the maximum is the highest observed moment; a percentile (P90, P95) is the level not exceeded in that fraction of moments; the design peak is the level the space is actually sized for, a design choice and not a measured result. A peak without its percentile is not a figure anyone can act on. "The peak was 71 per cent" means one thing at P90 and another at the absolute maximum.
Illustrative worked example: 600 people, one measured month
- Mean occupancy
- 44%
- P90
- 63%
- P95
- 68%
- Absolute maximum, the all-hands day
- 89%
Sizing on the mean provides for 264 people and fails every Tuesday and Wednesday. Sizing on P95 provides for 408 and fails on the all-hands day.
The all-hands day is a catering and logistics problem, not a floor-area problem. Building for it costs a permanent fifth of the floor plate to solve something that happens twice a year.
Where it goes wrong
Designing to the average
Half of all days are busier than the average day. A building sized on it is short of space half the time, which reads to the people in it as a building that does not work.
Designing to the maximum
One exceptional day sets a floor area that stands empty for the rest of the year. It is the most expensive way to be generous.
Not saying which percentile
Two studies quoting "the peak" can differ by twenty points because one took P90 and the other took the highest reading. State it every time the number is used.
Where this measurement decides something
- How much office space do we need?
Sizing a building on this figure.
- Consolidate or renew the lease?
Taking it to a board.
- Occupancy
How it is measured in practice.
Related terms
- Occupancy
The measure the percentile is taken across.
- Sharing ratio
What the peak, once chosen, actually determines.
- No-show rate
Why the observed peak can sit below the booked one.
Comparing two suppliers' occupancy figures?
Describe in a message how each supplier defines its occupancy figure, and we will tell you what each one is counting.