Start from the busiest day, not the headcount or the average, and the rule of thumb turns out to overstate the space by more than a quarter.
Size the desks for the busiest day, then add meeting space, support space and circulation per desk. An illustrative 200-person occupier with 70 per cent attendance on its peak day needs 140 desks and 1,552 m² of net internal area: 7.8 m² per employee, or 11.1 m² per desk. The familiar 10 m² per head applied to the headcount would take 2,000 m², 28.9 per cent more than the business uses.
Worked in full in Office Real Estate by Julian R. Sterling, with every figure reproduced in a free workbook.See the book on Amazon →
Occupiers ask this question before a lease event, and landlords should ask it too, because the answer sets how much of a building a tenant will renew. Since hybrid working, the headcount no longer decides the area. The peak day does.
| Input | Value |
|---|---|
| Headcount | 200 |
| Average daily attendance | 55% |
| Peak-day attendance (midweek) | 70% |
| Desk, with its secondary circulation | 6.0 m² |
| Meeting and collaboration seats per desk, at 2.5 m² each | 0.5 |
| Focus rooms or phone booths of 3.0 m², per desks | 1 per 10 |
| Kitchen and breakout per desk | 1.0 m² |
| Reception | 40 m² |
| Storage, print and IT per desk | 0.4 m² |
| Primary circulation, on the usable subtotal | 20% |
Every allowance is illustrative. A legal firm with cellular offices or a trading floor with large desks will sit at the top of any range; a contact centre at the bottom. The method carries over: per-desk allowances, a fixed reception, and circulation on top.
Step 1. Desks for the peak day. 200 × 70% = 140 desks, a desk ratio of 0.70 per person.
Step 2. Build the usable area from the desks.
| Zone | Calculation | m² | Share |
|---|---|---|---|
| Desks | 140 × 6.0 | 840 | 54.1% |
| Meeting and collaboration | 140 × 0.5 × 2.5 | 175 | 11.3% |
| Focus rooms | 14 × 3.0 | 42 | 2.7% |
| Kitchen and breakout | 140 × 1.0 | 140 | 9.0% |
| Reception | fixed | 40 | 2.6% |
| Storage, print, IT | 140 × 0.4 | 56 | 3.6% |
| Usable subtotal | 1,293 | ||
| Primary circulation | 1,293 × 20% | 258.6 | 16.7% |
| Net internal area | 1,551.6 | 100% |
Step 3. Divide.
Space per employee = NIA / headcount = 1,551.6 / 200 = 7.76 m², about 84 sq ft
Space per desk = NIA / desks = 1,551.6 / 140 = 11.08 m²
Excel: =(Desks*(6+0.5*2.5+3/10+1+0.4)+40)*(1+20%)/Headcount
Desks are only 54.1 per cent of the floor. The other 45.9 per cent is space that scales with the desks but is never counted when someone multiplies people by a desk footprint. That is why space per desk, 11.1 m², is the figure that travels between projects, and space per employee is an output of the attendance policy.
At an illustrative total occupancy cost of 943.04 per m² a year, rent, service charge, rates, annualised fit-out and running costs together, the 1,552 m² cost 1,463,221 a year, 7,316 per employee. Rent alone at 450 per m² is 698,220, or 3,491 per employee. The build-up of that 943.04 is in how much an office costs per desk per year.
| Peak attendance | Desks | NIA m² | m² per employee | Cost a year | Against base |
|---|---|---|---|---|---|
| 50% | 100 | 1,122 | 5.6 | 1,058,091 | -405,130 |
| 60% | 120 | 1,337 | 6.7 | 1,260,656 | -202,565 |
| 70% | 140 | 1,552 | 7.8 | 1,463,221 | 0 |
| 80% | 160 | 1,766 | 8.8 | 1,665,786 | 202,565 |
| 100%, a desk each | 200 | 2,196 | 11.0 | 2,070,916 | 607,695 |
Each ten points of peak attendance moves about 215 m² and 202,565 a year. Space per desk barely changes, from 11.2 to 11.0 m², because only the reception is fixed. The lever is the peak day, and a policy that spreads attendance across the week is worth more than any change to desk size.
There are two, in opposite directions. The first applies a per-head rule to the headcount: 200 × 10 m² = 2,000 m², 448 m² and 28.9 per cent more than the plan, or 422,859 a year of space that is never full. The second sizes on average attendance: 55 per cent gives 110 desks and 1,229 m², which looks efficient and leaves 30 people without a desk every Tuesday, until the occupier takes more space on worse terms. The right test reads both numbers: on the average day 110 people use a floor sized for 140, so desks are 78.6 per cent occupied and each person present has 14.1 m². That is the price of having a desk for everyone who comes in on the busiest day.
Check the measurement basis before comparing with a landlord's quote. These figures are net internal area. A building quoted on a gross or rentable basis will show a larger number for the same usable floor.
For a landlord, the same arithmetic is a forecast of how much space a tenant hands back at expiry, which the book prices into the re-letting cycle; the free workbook for this case carries those models. When a quote is on rentable rather than usable area, see how to calculate rentable square feet from usable.
It depends on how many people come in on the busiest day. On the illustrative plan each desk needs about 11.1 m² once meeting rooms, kitchen, storage and circulation are added. With one desk per person that is 11.0 m² per employee; at 70 per cent peak attendance it is 7.8 m², about 84 sq ft; at 50 per cent, 5.6 m².
Enough for the peak day, not the average. With 200 staff, 55 per cent average attendance and 70 per cent on the busiest midweek day, the plan needs 140 desks, a ratio of 0.70 desks per person. Sizing on the average gives 110 desks and leaves 30 people without one every Tuesday.
Only for an office with a desk for everyone. Applied to headcount in a hybrid office it takes 2,000 m² where the peak-day plan needs 1,552 m², 28.9 per cent too much. At an illustrative 943.04 per m² of total occupancy cost that is 422,859 a year of space nobody sits in.
This article is one calculation from Office Real Estate. The book takes the same case from first principles to the decision, chapter by chapter, and every figure it prints is a live formula in the free companion workbooks.
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