Shift Relief Factor and FTE Coverage Calculator
A post that must be staffed around the clock needs far more than one employee per shift. The relief factor is the multiplier that turns posts into heads after leave, holidays and training.
Your numbers
Stations or roles that must be covered every hour of operation.
168 for 24/7 operations, 120 for 24/5, 80 for two shifts of 5 days.
Your results
Assumes absence days are fully backfilled by the crew and ignores overtime, floaters and part-time staff.
Employees needed vs vacation days
Sweeps Vacation days per employee from 0 to 30, holding your other inputs fixed.
Absence data from payroll and ERP
Optional: we can compile absence and overtime history by department for a staffing review.
Optional. The tool and every export work without this. No spam.
How to use it
Enter the number of posts that must be staffed at all times and how many hours per week the plant runs. Add the paid hours per employee per week and the average days of vacation, holidays, sick leave and training they take. Choose the shift length so days convert to hours correctly. The result shows the relief factor, the number of employees needed and the annual cost.
- Use actual absence history, not policy maximums
- Run the model separately for 12-hour shift crews and 8-hour crews
- Include leave of absence and long-term injury if material
Formula
Relief factor equals the hours a post must be covered per year divided by the productive hours one employee delivers per year. Productive hours are paid hours less leave hours and training hours. For a 24/7 post that is 8,736 hours, and with about 1,800 productive hours per employee the factor is near 4.8, so one post needs nearly five people. Multiply by posts and round up to get heads.
Reading the result
The relief factor is the number every shift manager should know. A factor lower than expected usually means leave is under-estimated. Use the chart to see how vacation days change headcount, which helps in policy discussions. Where the rounded head count is above the unrounded figure by a large amount, part-time or floater coverage may be cheaper than a full extra position.
Common mistakes
Do not divide 168 hours by 40 and call it 4.2 people, since that ignores all leave. Do not mix shift lengths without adjusting days to hours, because a 12-hour shift day removes 12 hours of availability. Finally, if you run overtime to cover leave, the cost will differ from this model, so compare it with the overtime versus added shift calculator.
Frequently Asked Questions
What is a relief factor?
It is the ratio of the hours a position must be covered to the productive hours one employee provides. A factor of 4.8 means one continuously staffed post requires 4.8 full-time employees once leave and training are considered.
Why is the answer different for 12-hour shifts?
A leave day removes more hours on a 12-hour crew. Set the shift length input to match so that vacation, holiday and sick days convert to the correct hours. Paid hours per week may also differ for rotating patterns.
Does this work for 4 on 4 off or 2-2-3 patterns?
Yes for the totals, because it works from annual hours covered and annual hours delivered. It does not build the roster itself. Use a schedule template to check that the pattern gives enough crews on each day.
Should I include absenteeism beyond sick days?
Yes. Add unpaid absences, leave of absence and long-term disability in the absence days input if they are not backfilled elsewhere. Using last year's actual total from HR is more accurate than a policy figure.
If you want absence, leave and overtime data pulled from payroll and the ERP to calibrate this model, we can build that report for your plant.
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