The cost of an empty chair, attributed honestly

Two ways to count it

The usual calculation is the fee you did not collect. It is the right number for a business decision and the wrong one for understanding why this feels worse than it looks.

The second calculation is the one nobody does: what that hour cost to make available. Rent, equipment finance, the salary of whoever was standing there, the sterilisation, the insurance, the software subscriptions. Divide the annual total by the hours you actually offer, and you have a per-hour figure that was spent regardless of attendance.

The loss is the sum of both, and only the first of them appears in any report the practice produces.

Fixed cost per operating hour, worked through

A four-surgery dental practice, illustrative but built from realistic components. Annual figures divided by 1,760 operating hours — 44 weeks, 40 hours.

Cost	Annual	Per operating hour	Runs when the chair is empty?
Premises rent and rates	£68,000	£38.64	Yes
Clinical and admin salaries	£310,000	£176.14	Yes — staff are present
Equipment finance and maintenance	£42,000	£23.86	Yes
Insurance, indemnity, compliance	£29,000	£16.48	Yes
Software, utilities, everything else	£24,000	£13.64	Yes
Consumables	£46,000	£26.14	No — this is the only one that stops
Total	£519,000	£294.90	£268.76 of it runs regardless

Source: Illustrative model built for this page from typical UK practice cost structures. Not survey data; the point is the ratio between the last two columns, not the absolute figures.

Roughly 91% of the cost of an operating hour is incurred whether or not the patient arrives. That ratio, rather than any specific number, is why a no-show is more expensive than the missed fee suggests.

The three numbers that matter

of the per-hour cost in the model above runs whether or not anyone attends: 91%
spent to make one operating hour available, in that illustration: £269
the missed fee and the incurred cost are real, and only one gets reported: Both

Where this argument gets stretched too far

You cannot count the fixed cost as a loss — it was spent anyway.: Correct, and this is the strongest objection to the framing. The fixed cost is sunk, and an accountant would tell you the loss is the contribution margin on the missed appointment and nothing else. The reason the fuller figure is still worth knowing: it tells you what capacity costs, which is what you need when deciding whether to buy something that recovers it.
Staff can do other useful work in the gap.: Some of it, sometimes. Notes get written, sterilisation happens, a phone call is returned. What does not happen is the clinical work that only occurs with a patient in the chair, and that is the part the practice's revenue depends on.
Overbooking solves this.: It transfers it. Overbooking converts an occasional empty hour into an occasional overrun, and the cost moves from the practice's revenue to the patients' waiting time and the staff's day. It is a legitimate strategy and it is not free.
This model's numbers are made up.: The components are illustrative and stated as such. What is not made up is the structure: in any practice with premises, equipment and salaried staff, the overwhelming majority of an hour's cost is incurred before anyone walks through the door. Substitute your own figures and the ratio barely moves.

Working out your own per-hour figure

About an hour with last year's accounts. Do it once and it stays roughly true for a couple of years.

Total your annual costs, then remove consumables and lab feesThose are the only lines that genuinely scale with attendance. Everything else is capacity.
Count operating hours honestlyWeeks actually open, times hours actually offering appointments, times the number of chairs or rooms. Practices routinely overstate this by counting hours nobody was ever scheduled into.
Divide, and write the number somewhere visibleThis is the figure that makes an empty slot feel like a decision rather than a gap. Put it on the same page as the schedule.
Add your average fee to it for the full pictureCapacity cost plus foregone revenue. Neither alone is the answer and the sum is what a missed hour actually represents.
Recalculate when anything structural changesA new chair, a lease renewal, a clinician joining or leaving. Otherwise the number quietly stops being true.
Do not put the figure in a patient-facing messageIt is a management number. A reminder that mentions what the slot costs you reads as a threat and performs like one.

Questions

Should I use this number to set a no-show fee?

It tells you the ceiling of what the loss is, not what a fee should be. Fees that approach the true cost are unenforceable and damaging; fees that exist as a stated policy do most of their work by being stated.

What if the practice is running below capacity anyway?

Then the fixed-cost argument is stronger rather than weaker, because the unused capacity was already being paid for and the no-show adds to a pile that was not full. It also means your priority is demand rather than attendance.

Does this apply to solo practitioners?

The structure does, the ratio is milder. A therapist working from a room with low fixed costs loses mostly the fee, which is why the calculator on this site uses the fee rather than this fuller model as its default.

How does this compare to the missed fee?

In the illustration above the fee might be £90 and the capacity cost £269, so the fuller figure is roughly three times the reported one. In a low-overhead practice they can be about equal.

Tell me when this exists

In the context field: your per-hour figure if you work it out. I have not seen many of these.