One position that must be continuously occupied requires 24 × 7 = 168 coverage hours each week. With a 40-hour full-time weekly baseline, the arithmetic minimum is 168 ÷ 40 = 4.2 FTE before allowing for leave, training, breaks that require relief, or other time away from the position. That figure is a starting point for planning, not a complete roster.
The word “position” matters. This example requires one qualified person present at all times. If two people must be present continuously, the coverage requirement doubles to 336 hours per week. If demand varies by interval, calculate the requirement interval by interval rather than applying a single constant staffing level to the entire week.
Calculate the base coverage requirement
Start with hours of operation multiplied by the number of people needed at each time. For one continuously occupied position, seven days at 24 hours produces 168 hours. For one position operating 16 hours each day, the equivalent weekly requirement would be 112 hours. Document the operating pattern before discussing headcount.
Divide required coverage hours by the compatible full-time schedule. At 40 hours per week, 168 hours equals 4.2 FTE. At 37.5 hours per week, it equals 4.48 FTE. The coverage requirement has not changed; the denominator used to express it as an equivalent has changed.
The FTE calculator can check this ratio. The coverage-hours guide helps define the numerator. Keep those two steps separate so a later change to the full-time schedule does not accidentally change the underlying service requirement.
Add relief for time away from the position
Suppose the planning model assumes that 20% of scheduled hours will be unavailable for this specific coverage because of included leave, training and other activities. The remaining available share is 80%. Required scheduled hours become 168 ÷ 0.80 = 210 hours per week. At a 40-hour baseline, that is 5.25 scheduled FTE.
The 20% is an illustrative assumption, not a recommended benchmark. Estimate your own rate using relevant records and clear definitions. Include only activities that remove someone from the position and require replacement coverage. If an activity can genuinely occur while the position remains covered, treating all of it as lost coverage could overstate the requirement.
Do not calculate 168 × 1.20 and assume it is equivalent. That gives 201.6 scheduled hours, of which 80% is only 161.28 available hours. Dividing by the available share accounts for the fact that relief staff also have some unavailable time under the same assumption.
Test several availability assumptions
At 10% unavailable time, the required schedule is 168 ÷ 0.90 = approximately 186.67 hours, or 4.67 FTE on a 40-hour basis. At 15%, the requirement is about 197.65 hours, or 4.94 FTE. At 25%, it becomes 224 hours, or 5.6 FTE.
These scenarios show how sensitive the plan is to the availability assumption. They do not establish which rate is correct. Use the staffing shrinkage calculator to test assumptions, and keep the source of each assumption visible. A historical average, a forecast and a stress scenario should not be presented as if they were the same kind of evidence.
Check for double counting. If your productive-hours denominator has already removed leave and training, dividing again by an availability share that includes those same activities applies the deduction twice. Choose one consistent model and show the steps so another reviewer can identify what has already been included.
Convert aggregate hours into an actual roster
A requirement of 5.25 FTE does not mean five people automatically cover the position. It expresses hours relative to a baseline. Those hours must still be distributed across every interval with the right skills and any applicable scheduling constraints. Five full-time people on 40-hour schedules provide 200 scheduled hours before the example's availability adjustment, which is below the 210-hour requirement.
A mix of full-time and part-time schedules could supply the aggregate hours, but the timing matters. If all additional availability occurs during weekday mornings, it cannot fill a recurring night or weekend gap. The coverage gaps guide explains why sufficient total hours can coexist with uncovered intervals.
Build a dated roster and inspect coverage by interval. The shift coverage calculator can help identify gaps and overlaps for the schedule entered. Treat aggregate FTE as a capacity check and the roster as the test of whether that capacity appears where it is needed.
Include handover and break relief explicitly
If each shift change requires two people to overlap for 15 minutes, the extra scheduled time depends on how many handovers occur. Three handovers per day create 45 overlap minutes per day, or 5.25 hours per week. If that overlap is additional to the continuously occupied position, add it to the requirement rather than assuming it fits inside the original 168 hours.
Break relief also needs a clear definition. If the position cannot be left unattended and the assigned person must step away, someone else must cover that interval. Whether breaks are paid is a separate question from whether the operational position needs relief. Do not merge those two decisions into a single unexplained deduction.
Use the break coverage guide to organize overlapping assignments. Count each relief hour once. If the same hour already appears in a separate relief role or in the unavailable-time assumption, adding it again can inflate the total requirement without providing additional actual coverage.
Plan for variation, not only the average
A weekly average can conceal concentrated absences. Two people may be unavailable during the same week even if annual average availability looks sufficient. A practical plan should show how the operation handles ordinary variation, planned leave clusters and a reasonable disruption scenario, using assumptions appropriate to the service.
Keep the baseline requirement separate from the contingency arrangement. For example, the baseline may rely on a regular relief schedule while an unexpected absence requires a qualified backup. Identify whether that backup is actually available during nights and weekends rather than assuming every person on a contact list can fill every gap.
Do not claim that a particular staffing count guarantees continuity. The result depends on the roster, qualification coverage, absence patterns and the operational rules. Test those conditions directly, then describe what the plan covers and which exceptions require a separate response.
Check annual and calendar-based estimates
Multiplying 168 weekly hours by 52 gives 8,736 hours, but a 365-day year contains 8,760 hours. A 366-day year contains 8,784 hours. The difference appears because a calendar year contains more than exactly 52 weeks. For a full-year continuous-coverage budget, count the actual dates rather than treating 52 weeks as the entire year.
Keep the annual denominator equally clear. An annualized 2,080-hour full-time convention may be useful for expressing a budget, but it is not automatically the number of productive coverage hours one employee supplies. Leave, training and the actual scheduling calendar still need consistent treatment.
For operational rosters affected by daylight saving time, local clock shifts need date and offset context. A weekly average is not a substitute for checking the actual transition dates. Keep the schedule's time zone explicit so repeated or skipped local clock hours are handled intentionally.
Frequently asked questions
Are four people enough for one 24/7 position?
Four people each supplying 40 hours provide 160 hours, which is eight hours short of the 168-hour weekly requirement before any relief allowance. Different schedules could change the arithmetic, but the actual roster and relevant constraints still need checking.
Can I simply round 4.2 FTE up to five people?
Rounding can be a first budgeting step, but it does not prove sufficient coverage. Five 40-hour schedules provide 200 hours. Under the illustrative 20% unavailable-time assumption, only 160 hours remain for the position, still below 168.
What should I calculate first?
Start with required coverage by interval, then estimate available hours and build the roster. Use the Workforce Planning hub for supporting tools. Beginning with a desired headcount and forcing the assumptions to fit it can hide the very gaps the calculation is meant to reveal.