By Intious · Updated September 10, 2026
Divide productive workload by the available fraction of scheduled time, then divide by the full-time baseline to estimate required FTE.
Try the calculator with your own figures.
Define the denominator first
For this planning model, shrinkage is the share of scheduled hours that cannot be used for the target work. Calculate it as unavailable hours divided by scheduled hours, multiplied by 100. For 80 unavailable hours within a 400-hour schedule, shrinkage is 20%. Decide whether the schedule includes leave, breaks and training before measuring the unavailable portion. A denominator that changes between reports makes percentages difficult to compare.
Divide demand by availability
The available fraction is 1 minus the shrinkage rate expressed as a decimal. At 20% shrinkage, it is 0.80. To deliver 360 productive hours, schedule 360/0.80 = 450 hours. Multiplying demand by 1.20 would give only 432 scheduled hours, which produces 345.6 productive hours after 20% shrinkage. Dividing by availability is necessary because shrinkage is a fraction of the resulting schedule, not a surcharge on productive demand.
Translate required hours into FTE
With a 40-hour weekly baseline, 450 scheduled hours corresponds to 11.25 FTE. If the existing schedule supplies 400 hours, it has 10 FTE and needs another 1.25 FTE of scheduled capacity under the same assumptions. That does not automatically mean hiring two people. The additional hours might be distributed across part-time roles or changes to assignments, provided the arrangement covers the actual times and skills needed.
Compare a range instead of treating one rate as certain
For demand of 360 hours, 10% shrinkage requires 400 scheduled hours, 20% requires 450 and 25% requires 480. At a 40-hour baseline those are 10, 11.25 and 12 FTE. The difference is material, so use evidence from comparable weeks and document any expected changes in absence or training. A peak week and an ordinary week may need separate scenarios rather than one average rate.
Check overlap and operational constraints
Do not count a training hour again as a meeting hour, or remove leave twice if it is already absent from scheduled hours. After the weekly calculation, examine daily coverage, skills, peaks and minimum staffing. The arithmetic does not forecast queue delays or establish service-level staffing. It provides a transparent capacity estimate that should be reconciled with the operating schedule.
Frequently asked questions
Why is 100% shrinkage invalid?
It leaves zero productive time, so positive demand cannot be met with any finite number of scheduled hours.
Can I add shrinkage percentages together?
Only when they use the same denominator and represent non-overlapping time. Otherwise add or deduplicate the underlying hours before calculating the combined percentage.
Does FTE equal headcount?
No. FTE expresses scheduled hours relative to a full-time baseline. Headcount counts people regardless of their individual schedules.