Planning for unplanned absence: the shrinkage you can’t schedule
The shrinkage that fights back
Most shrinkage is planned: holiday, training, meetings, breaks. You know it’s coming and you build it in. Unplanned absence — sickness, no-shows, emergencies — is the awkward one, because it lands without notice, on exactly the days you can least afford it, and it varies far more than the planned categories. Treating it as a flat percentage in the shrinkage stack is the single most common reason a roster that looked fully covered turns into an understaffed morning.
Plan for the distribution, not the average
Unplanned absence has an average, but the average is the least useful thing about it. What hurts is the variance and the correlation: absence clusters — Mondays, winters, the day after a big event, the height of a flu season — so the bad days are much worse than the mean suggests, and they often coincide with high demand. Planning to the average leaves you short on precisely the days that matter. The better approach is to understand the shape of your absence: its typical level, how high the bad days run, and when they cluster, then decide deliberately how much of that risk you buffer against and how much you flex against on the day.
Buffer some, flex the rest, manage the cause
Three levers, used together. Buffer a portion of the expected variation into the plan — a deliberate, costed amount of slack on the days and seasons you know run hot, rather than a flat uplift that over-pays on the good days. Flex the residual on the day with the levers you already hold — overtime, swaps, moving deferrable work — so you’re not buffering against the very worst day every day. And manage the cause, because a chunk of unplanned absence is a symptom: punishing schedules, low engagement and burnout all show up first as sickness. A return-to-work conversation and a humane roster do more for your absence line than any buffer. Plan absence as a distribution you partly buffer and partly flex against — not a flat number you bolt on and hope.
Try the absence buffer calculator, then pair this with the shrinkage deep-dive, the shrinkage calculator, and psychological safety.