The minimum staff for a 24/7 NOC.

Five people cover the clock. Nobody covers a sick day.

A week is 168 hours and a full time week is 40, so around the clock coverage needs 4.2 people, which rounds up to five. Five is also where the honest part starts. At five, every hour of the week has exactly one person on it, so a meal break, a training morning or one person's leave is time with nobody at the desk.

Start with two numbers. A week is 168 hours. A full time week is 40. Divide one by the other and you get 4.2, which is how many people it takes to have somebody at the desk at all times, before anybody takes a day off. You cannot hire 0.2 of a person, so the answer rounds up to five.

Four people supply 160 hours against a demand of 168, so at least 8 hours of every week have nobody on before anyone has picked a shift pattern. In practice it is worse than that, because shifts come in whole blocks on whole days. The pattern the calculator draws for four people covers 144 hours and leaves 24, and all 24 of them are at the weekend.

Five is the first headcount where the week has no holes in it. Three eight hour shifts, Days, Swing and Nights, running all seven days, with each person taking four or five of them. Nobody goes past 40 hours and every hour of the week has somebody on it.

Then read the second line the calculator prints. All 168 of those hours have exactly one person on. That is not a rota drawn badly, it is what five people and 168 hours means. A meal break empties the desk for the length of the break. A training morning empties it for the morning. There is nobody to hand to, because there is nobody else on.

The four rows below are the whole decision. The middle column is what a headcount can reach, the one beside it is how thin it is while it reaches it, and the last one is what happens the first time somebody is away.

Read the last two columns together. Five people cover the whole week, and all 168 of those hours have one person on. Take any one of the five out and the remaining four are short by 8 hours. Six is the first headcount with any slack, because the rest can still cover the week, and it takes the hours with one person on down to 128. Seven takes them to 112 and breaks up the long stretches, from a longest unbroken solo run of 168 hours down to 16.

Take one of the five out for a week, for leave or for illness, and the other four can be rostered at most 40 hours each. That is 160 hours against the same 168. They are 8 hours short, and no amount of moving shifts around changes it.

In practice somebody usually covers it on overtime, and that does lower the severity, because a paid hour is not an empty one. It is not a fix though. Overtime has to be offered and accepted, so some weeks nobody takes it and the hours are simply uncovered. And a rota that needs it every time somebody is away is not covering the week, it is borrowing against the four people who are left.

This is the same 4.2 arriving from the other direction, and it is the honest reason to hire a sixth. A sixth person does not buy coverage, because five already reaches every hour. What six buys is the first slack in the plan. When somebody is away, the rota falls back to the five person shape for that week instead of leaving a hole, and in a normal week it takes the hours with one person on down from 168 to 128.

The ladder has a ceiling, and naming it is what makes the rest of it believable. On a 40 hour week the ceiling is eleven. At eleven, every hour of the week already has two people on, so a twelfth person adds depth where the load is rather than hours nobody had. A calculator that answers hire one more at every number is a sales tool, and it gets read as one.

Whatever number you land on, some hours have one person and some may have none. Alerts keep arriving in both. The question a rota cannot answer is what happens to them between the moment they arrive and the moment somebody is back at the desk.

That is worth saying plainly, because it is the part that gets waved away in a staffing plan. An empty chair does not make the night quiet. It makes the night unwatched.

Signal9 is alert and on call software for operations teams, and the coverage calculator is a free tool from it, which is why it names what a headcount cannot do as well as what it covers. For the hours with one person on, alerts arrive in one shared view instead of four consoles somebody has to keep checking. For the hours with nobody on, automation acts on the alerts it has been told it can act on, and the alerts you marked most urgent keep escalating until somebody answers. Neither of those is a person at the desk, and we do not describe them as one.

What is the minimum staff for a 24/7 NOC? Five people, on a 40 hour week. A week is 168 hours, so 168 divided by 40 is 4.2, and four people cannot reach every hour however the shifts are arranged. Five covers all 168 with one person on at a time, which makes it the minimum rather than the comfortable answer.

Can four people cover 24/7? Not for a full week. Four people supply 160 hours against 168, so at least 8 hours have nobody on before anyone picks a shift pattern. A practical four person rota does worse, because shifts come in whole blocks on whole days. The one the calculator draws covers 144 hours and leaves the weekend nights empty.

How many people do you need for 24/7 including holidays and sickness? Six is the first headcount with any slack. At five, one person away leaves the other four 8 hours short of the week, because four times 40 is 160 and the week is 168. Those hours get covered on overtime, if somebody takes it, and uncovered if nobody does. At six the rota can fall back to the five person shape instead, which is why the sixth person buys resilience rather than coverage, and why part of what they cost is already being paid in overtime.

How many hours a week is 24/7 coverage? 168 hours, which is seven days at 24 hours each. Against a 40 hour week that is 4.2 people of pure supply, before any allowance for leave, training, breaks or handover.