Absence Rates Project Time Calculator Examples
Worked project capacity examples showing how absence rates and contingency can change estimated completion time.
These examples use different team sizes, workloads, and absence assumptions. They show why the same amount of work can require a different timeline when expected productive capacity changes.
Small team with no contingency
A three-person team needs to complete 360 productive work hours. Each person is scheduled for 35 hours per week, and the expected absence rate is 5%.
Input Summary
Project work
360 hours
Team size
3 people
Hours per person
35 hours per week
Absence rate
5%
Contingency
0%
Calculation Breakdown
- 1Scheduled capacity3 × 35105 hours per week
- 2Available capacity105 × (1 − 5 / 100)99.75 hours per week
- 3Project duration360 ÷ 99.753.61 weeks
Result Summary
Project duration
3.61 weeks
Absence Rates Project Time Calculator
The project is estimated to take about 3.6 weeks, compared with 3.4 weeks at full scheduled capacity.
Five-person team with absence and contingency
Five people are scheduled for 40 hours weekly to deliver 800 hours of work. The plan allows for 8% absence and 10% contingency.
Input Summary
Project work
800 hours
Team size
5 people
Hours per person
40 hours per week
Absence rate
8%
Contingency
10%
Calculation Breakdown
- 1Scheduled capacity5 × 40200 hours per week
- 2Available capacity200 × (1 − 8 / 100)184 hours per week
- 3Duration before contingency800 ÷ 1844.35 weeks
- 4Final duration4.35 × (1 + 10 / 100)4.78 weeks
Result Summary
Final duration
4.78 weeks
Absence Rates Project Time Calculator
The estimate is about 4.8 weeks, versus a 4.0-week full-capacity baseline.
Larger team with higher absence
An eight-person team works 37.5 hours each per week on a 2,400-hour project. The average absence rate is 12%, with no extra contingency.
Input Summary
Project work
2,400 hours
Team size
8 people
Hours per person
37.5 hours per week
Absence rate
12%
Contingency
0%
Calculation Breakdown
- 1Scheduled capacity8 × 37.5300 hours per week
- 2Absence hours300 × 12 / 10036 hours per week
- 3Available capacity300 − 36264 hours per week
- 4Project duration2400 ÷ 2649.09 weeks
Result Summary
Project duration
9.09 weeks
Absence Rates Project Time Calculator
The project is estimated to take about 9.1 weeks instead of 8.0 weeks without absence.
Short deadline with a high absence assumption
Two people have 30 scheduled hours each per week to complete 300 hours of work. The plan assumes 20% absence and 15% contingency.
Input Summary
Project work
300 hours
Team size
2 people
Hours per person
30 hours per week
Absence rate
20%
Contingency
15%
Calculation Breakdown
- 1Scheduled capacity2 × 3060 hours per week
- 2Available capacity60 × (1 − 20 / 100)48 hours per week
- 3Duration before contingency300 ÷ 486.25 weeks
- 4Final duration6.25 × (1 + 15 / 100)7.19 weeks
Result Summary
Final duration
7.19 weeks
Absence Rates Project Time Calculator
The project is estimated to take about 7.2 weeks, compared with 5.0 weeks at full scheduled capacity.
How to Read Your Results
Available weekly capacity is the estimated productive time remaining after the absence allowance.
Hours lost to absence shows the average weekly reduction, not a prediction of which individuals will be absent.
The base duration is a full-scheduled-capacity benchmark rather than a likely delivery date.
Additional weeks compare the final estimate with the no-absence, no-contingency baseline.
Round estimates appropriately for planning; a decimal week may need conversion into milestones or working days.
Assumptions & Important Notes
- All team members in each example are assumed to contribute at the same scheduled weekly hours.
- The project workload is measured in productive work hours.
- Absence is averaged across the project rather than assigned to specific dates or people.
- Examples are estimates for planning purposes, not delivery commitments.
Related Examples
Frequently Asked Questions
Should I use a different absence rate for each project?
It can be useful when project periods, teams, seasonal patterns, or planned leave differ. Use an assumption that fits the period being considered.
Can I use decimal weekly hours?
Yes. A weekly schedule such as 37.5 hours can be used because capacity is calculated from the entered hours.
Why are the results shown in weeks rather than days?
The calculator starts with weekly capacity, so the duration is naturally expressed in weeks. You can convert it using your organisation's working-week pattern if needed.
Does a larger team always shorten the estimated duration?
The simple capacity calculation says more scheduled productive hours reduce duration, but real projects can also have coordination, training, and dependency constraints.
Ready to calculate your own result?
Use the live calculator with your own inputs, timing, and preferences.