Contribution Margin (per occupied bed)
Definition
Contribution margin is what one occupied bed adds toward covering fixed costs: the rent it earns minus the variable costs that exist only because that resident does, such as marginal utilities, cleaning consumables and payment fees. It is the building block of any honest break-even calculation.
The formula
Contribution margin = Net effective rent per bed − Variable cost per occupied bed
- Net effective rent
- the rent actually collected over the stay, after discounts, free weeks and incentives, divided by the months of the stay
- Variable cost
- costs that only exist because the bed is occupied — incremental utilities, consumables, laundry, payment fees, turnover cleaning amortised over the stay
Worked example
Our worked example: a room advertised at £950 with the first month free on a 12-month stay, in a building where an occupied bed adds about £85 a month in incremental cost.
- 01Cash collected over the term = £950 × 11 = £10,450.
- 02Net effective rent = £10,450 ÷ 12 = £870.83.
- 03Contribution margin = £870.83 − £85 = £785.83 per occupied bed per month.
- 04Using the headline £950 instead would have produced £865 — a 10% overstatement.
That 10% error does not stay at 10%. Break-even occupancy divides fixed costs by contribution margin, so an overstated margin understates the occupancy you actually need — and it does so in exactly the direction that makes a marginal deal look safe.
Contribution margin answers a narrow question precisely: what does filling one more bed contribute toward covering the costs that exist whether or not it fills. It is not profit and it is not meant to be. Its entire purpose is to be the denominator in the break-even calculation, and everything about how it is constructed should serve that.
In coliving the split between fixed and variable is unusually lopsided, and that is why the metric matters here more than in hospitality. A hotel's costs move meaningfully with occupancy — housekeeping, breakfast, laundry per stay. A coliving building's largest costs are rent or debt, staff and compliance, none of which move at all. The consequence is a high contribution margin and a break-even that is reached and then leveraged hard: the beds above break-even are almost pure margin, which is why the last 15% of occupancy is worth disproportionately more than the first 15%.
Track it per building rather than blended across a portfolio. A blended contribution margin hides the building that is carrying the others, and the decision it is supposed to inform — whether to discount to fill a specific room this month — is always a single-building decision.
The common mistake
Putting fixed costs into the variable column
Rates, insurance, the head rent, the community manager's salary and the broadband line do not change when one more room fills, so none of them belong in variable cost. Including them produces a contribution margin that is far too low, which pushes break-even occupancy above what the building can achieve and can kill a viable deal on paper. The test for each cost line is simple: if this bed stayed empty for a month, would this cost disappear?
Frequently asked
Should turnover cleaning be a variable cost?+
Yes, but amortised over the stay rather than charged in the month it happens. A deep clean between residents only occurs because the bed was let, so it is variable; charging the whole cost to one month makes that month's margin meaningless. Divide it by the average stay length in the building.
Is contribution margin the same as gross margin?+
No. Gross margin is a whole-business ratio over a period; contribution margin is a per-unit figure for one additional occupied bed. They can point in different directions, and the per-unit number is the one that tells you whether accepting a discounted resident is better than leaving the room empty.
Can contribution margin be negative?+
Rarely in coliving, and if it is, the discount has gone past the point where filling the room helps at all. That is the one situation where holding a room empty is the better decision, because every month it is occupied makes the loss larger rather than smaller.
Break-even occupancy calculator
Read →
Net effective rent explained
Read →