Absence Rates Project Time (Individual) Calculator Examples
See worked examples of how expected absence changes an individual project’s scheduled days, extra time and total hours.
These examples show how the same method works for short tasks, longer assignments, and different expected absence rates. All results are scheduled working time, not calendar dates.
Short task with low expected absence
A single employee needs to complete a focused 10-day work assignment and has an expected absence rate of 5%.
Input Summary
Planned productive work days
10 days
Expected absence rate
5%
Working hours per day
7.5 hours
Calculation Breakdown
- 1Attendance rate100% - 5%95%
- 2Adjusted project days10 / 0.9510.5 working days
- 3Extra time10.5 - 100.5 working days
- 4Scheduled hours10.5 * 7.578.9 hours
Result Summary
Scheduled hours
78.9 hours
Absence Rates Project Time (Individual) Calculator
Allow about 10.5 scheduled working days and 78.9 scheduled hours.
Standard project with typical absence allowance
An employee has 20 productive days of project work and an expected absence rate of 8%.
Input Summary
Planned productive work days
20 days
Expected absence rate
8%
Working hours per day
8 hours
Calculation Breakdown
- 1Attendance rate100% - 8%92%
- 2Adjusted project days20 / 0.9221.7 working days
- 3Extra time21.7 - 201.7 working days
- 4Scheduled hours21.7 * 8173.9 hours
Result Summary
Scheduled hours
173.9 hours
Absence Rates Project Time (Individual) Calculator
Plan for about 21.7 working days, including 1.7 additional days.
Long assignment with higher expected absence
An individual is assigned 45 productive work days on a project with eight-hour working days.
Input Summary
Planned productive work days
45 days
Expected absence rate
12%
Working hours per day
8 hours
Calculation Breakdown
- 1Attendance rate100% - 12%88%
- 2Adjusted project days45 / 0.8851.1 working days
- 3Extra time51.1 - 456.1 working days
- 4Scheduled hours51.1 * 8409.1 hours
Result Summary
Scheduled hours
409.1 hours
Absence Rates Project Time (Individual) Calculator
Plan for approximately 51.1 scheduled working days and 409.1 scheduled hours.
Part-time daily hours with substantial absence risk
An individual needs six productive days for a task but has limited expected availability during the project period.
Input Summary
Planned productive work days
6 days
Expected absence rate
20%
Working hours per day
6 hours
Calculation Breakdown
- 1Attendance rate100% - 20%80%
- 2Adjusted project days6 / 0.807.5 working days
- 3Extra time7.5 - 61.5 working days
- 4Scheduled hours7.5 * 645 hours
Result Summary
Scheduled hours
45 hours
Absence Rates Project Time (Individual) Calculator
Allow 7.5 scheduled working days and 45 scheduled hours.
How to Read Your Results
Estimated project time is the number of scheduled working days to allow, not the final calendar date.
Extra time to allow is the difference between the original productive effort and the adjusted scheduled duration.
Expected absence time is the estimated unavailable portion within the adjusted schedule.
Total scheduled hours include both productive work hours and hours expected to be lost to absence.
Add weekends, holidays, planned leave and project-specific delays separately when setting dates.
Assumptions & Important Notes
- Absence is distributed evenly through each example’s scheduled work period.
- The productive work requirement does not change because of absence.
- Work can resume after an absence without additional restart or handover time.
- Working hours are consistent from one scheduled day to the next.
Related Examples
Frequently Asked Questions
Can I use these examples with a different number of hours per day?
Yes. Recalculate total scheduled hours using your usual hours per day. The adjusted number of workdays is unchanged when planned days and absence rate stay the same.
Do these examples include annual leave?
Only if annual leave is included in the absence-rate assumption. Specific planned leave can also be added separately to the working calendar.
Why does a 20% absence rate add more than 20% to project time?
Only 80% of scheduled time is available. Six productive days therefore need 6 divided by 0.80, or 7.5 scheduled days.
Should project time be rounded up?
For scheduling, it can be practical to round to a suitable planning increment, such as a half-day or full day, while keeping the unrounded figure for reference.
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