Project Timeline Calculator
Duration with buffer and part-time staff.
Enter your values
ⓘ Live results
Results
- Duration
- 9.6 weeks
- Months
- 2.2
- Team capacity per week
- 112 h
- Buffer added
- 1.6 weeks
Quick answer
Calendar duration is effort divided by effective capacity, plus a risk buffer.
Weeks = effort hours ÷ (people × available hours)
How to use the Project Timeline Calculator
- 1Enter total estimated effort in hours.
- 2Enter team size and realistic weekly hours.
- 3Add a risk buffer.
Worked example
Using the values the calculator loads with:
Inputs
- Effort900 hours
- Team size4
- Available hours per week28
- Risk buffer20 %
Results
- Duration9.6 weeks
- Months2.2
- Team capacity per week112 h
- Buffer added1.6 weeks
Frequently asked questions
Why not 40 hours per person?
Meetings, support and admin usually leave 25–30 productive hours.
Does adding people speed it up?
Only up to a point — coordination cost grows with team size.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.