How Many of 12 Staff Can Be Off at Once?
A team of 12 just clears the third-person boundary: 9 on shift, 3 spare, and about 14.3 short days a year where a team of 11 carries 40.1.
Three of a team of 12 can be on leave at once. With 9 people required on shift, headroom is 3, and the model expects the team to fall below that minimum on about 14.3 working days a year out of 261. Run a whole year at peak-period pressure and the same rate works out at about 55.2 days.
How often that many are actually away
The average is 1.52 people away, and averages do not break rosters. What breaks a roster is the tail: the days when more people than usual are off at the same time. With 12 people each away on 12.6 percent of working days, this is how a year of 261 days is expected to distribute.
Everything below 4 away fits inside the roster. Everything from 4 up is a day the operation runs under its minimum of 9, and those add up to about 14.3 days a year.
What is hard about 12
A team of 12 sits just past a step rather than just below one, and that is the single most useful fact about this size. Both 11 and 12 have to put 9 people on shift, so the twelfth person adds no obligation at all, only headroom, and takes the team from 2 spare to 3. Nothing about the leave policy changes across that boundary. At 11 the model expects about 40.1 short days a year. At 12 it expects about 14.3. The whole difference is one head standing behind an unchanged minimum.
The next step up is a long way off, and the ground between here and there slopes the wrong way. Headroom only moves again at 16, where 4 can be off and the expectation falls to about 11.1 short days. A team of 14 still gets headroom of 3, but it has to field 11 on shift, and two more people each carrying a 12.6 percent daily chance of being away push the expectation up to about 23.6 days. So 12 is the best covered size anywhere below 16, and it beats 18 at 17.6 as well. Hiring a thirteenth or fourteenth person buys throughput and loses cover unless the minimum on shift comes down with the hire.
Averages hide all of this. On a normal day the model puts 1.52 people away against headroom of 3, which reads as comfortable. In a peak period the average rises to 2.43, which sits just under the line, and that is why the peak rate works out at about 55.2 days rather than 14.3. The model also assumes people book leave independently of each other, which is the assumption most generous to the roster, because real requests pile onto school holidays and the last fortnight of December. Every figure here is a floor on the real risk, and the team still has 300 person-days of annual leave to place across a year that holds only 261 working days.
Move the minimum, move the answer
The team size is usually fixed. The minimum on shift often is not, and it is the faster lever: making one role coverable for a day changes the arithmetic more than a hire does.
| Minimum on shift | Can be away | Short days a year |
|---|---|---|
| 11 | 1 | 119.9 |
| 10 | 2 | 48.7 |
| 9assumed | 3 | 14.3 |
| 8 | 4 | 3.1 |
| 7 | 5 | 0.5 |
| 6 | 6 | 0.1 |
What this assumes, and where it is generous
These figures treat each person as independently likely to be away, which is the assumption most favourable to the roster. Real leave clusters: school holidays, the last fortnight of December, and the local summer shutdown pull requests onto the same dates. Treat every number here as the best case, and the peak column as a reminder of how far the real case sits from it.
Run the same team at a peak concentration of 1.6 times the ordinary rate, which is a stated planning assumption rather than a measured figure, and the expected count away rises from 1.52 to 2.43. Held across a full year, that rate would imply about 55.2 short days rather than 14.3. Real years are neither, but the gap between the two is the size of the scheduling problem that leave clustering creates.
The inputs are 25 days of paid annual leave and 8 days of average sickness per person. Both vary by country, and the relief factor library carries sourced figures for 17 of them, from zero statutory leave in the United States to 28 days in the United Kingdom. Swap your own numbers in and the shape of the distribution holds even as the counts move.
What to do with this
Approve 3 concurrent absences and stop there, because the fourth is the one that drops the team below its minimum of 9.
Backfill any vacancy before the next peak, since running at 11 against the same minimum of 9 moves the expectation from about 14.3 short days a year to about 40.1.
Hold peak-period approvals under the full 3, when the model already puts 2.43 people away on an average day.
Common questions
- How many people can be off at once in a team of 12?
- Three. With 9 required on shift, a team of 12 carries headroom of 3, so a fourth concurrent absence is what leaves the shift short. Across 261 working days the model expects that on about 14.3 of them, and because it assumes leave requests are independent of one another, 14.3 is a floor rather than a forecast.
- Would hiring one or two more people improve cover?
- Not at first. A team of 14 still has headroom of 3, because the minimum on shift rises to 11, and the two extra people each carry the same 12.6 percent daily chance of being away, so expected short days rise to about 23.6. Cover only improves again at 16, where headroom reaches 4 and the expectation falls to about 11.1 days a year.
- What happens if the minimum on shift changes?
- It dominates every other lever. Holding 10 on shift leaves headroom of 2 and about 48.7 short days a year, holding 9 leaves headroom of 3 and about 14.3, and dropping to 8 leaves headroom of 4 and about 3.1. One person taken off the minimum line is worth more than several added to the payroll.
Your next schedule could take 2 minutes.
Import your team, set your rules, hit auto-fill. Most teams are live the same day.
30 days free ยท No credit card required
Already have an account?Sign in
