Shift Cover Headcount Calculator

Seven days, two shifts a day, two people on each. Twenty-eight shifts a week, and five shifts each, so five point six people.

You need six point six five.

The naive figure assumes everybody is present every week of the year. Nobody is. Twenty-eight days of holiday against a two-hundred-and-sixty-day year is nearly eleven per cent on its own, and with sickness and training it comes to fifteen and three quarters. That is not an unlucky year — it is a normal one.

The fix is not to add ten per cent and hope. It is to divide by the share of the year people are actually there, and those are different arithmetic: the gap between them grows as unavailability rises, which is exactly when a rota is under most strain.

Six point six five rounds to seven, which is one more person than the shift count suggests. That person is the difference between a rota that works and one that runs on overtime and goodwill — and the overtime costs more over a year than the person would have.

The table runs the same rota at every holiday entitlement, so you can see what an extra week of leave does to the headcount before you agree to it rather than afterwards.

Rounding up is not padding. You cannot employ two thirds of a person, and a rota short by a third of one is a rota covered by overtime every single week.

If you tell it nobody is ever available it refuses to answer rather than dividing by nothing, which is the correct response to that.

What it does not know is whether your shifts can be part-covered, whether people can work across roles, and whether a quiet shift genuinely needs the full complement. All three reduce the answer, none of them is arithmetic, and all three are decisions about how the work is organised rather than sums — so they belong to you.

Save as many versions as you like and put any two side by side, figure against figure, with the better one on each line marked and the difference in its own column. That screen is the one that decides things, and it is the part a free calculator cannot do at all. A seven-day operation and a five-day one are different problems, and the difference is not five sevenths.

One HTML file. No account, no subscription, no internet needed. Opens on Windows, Mac and Android; the readme explains the extra step on iPhone and iPad, where Apple blocks JavaScript in downloaded files and every tool of this kind is affected.

Everything lives in your browser on your device. Nothing is uploaded, which is why it works offline and why nobody else can see your figures — and it also means clearing your browsing data deletes it. The tool does not pretend otherwise: the header shows how long since your last export at all times, turns amber after three days and red after seven, and export is one click that produces a plain file you keep.