Project Timeline Calculator
Duration with buffer and part-time staff.
Enter your values
Enter the effort in hours.
Enter the team size you are working with.
Enter the available hours per week you are working with.
Enter the risk buffer in %.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- 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)
At a glance
| What it does | Duration with buffer and part-time staff. |
|---|---|
| Category | Technology |
| Inputs needed | Effort, Team size, Available hours per week, Risk buffer |
| Main output | Duration |
| Formula | Weeks = effort hours ÷ (people × available hours) |
| Cost | Free — no sign-up, no download |
How to use the Project Timeline Calculator
- 1Enter total estimated effort in hours.
- 2Enter team size and realistic weekly hours.
- 3Add a risk buffer.
Inputs explained
- Effort(hours)
- Enter the effort in hours.
- Team size
- Enter the team size you are working with.
- Available hours per week
- Enter the available hours per week you are working with.
- Risk buffer(%)
- Enter the risk buffer in %.
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.
What do I need to enter into the Project Timeline Calculator?
Just 4 values: effort, team size, available hours per week, risk buffer. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Project Timeline Calculator work out the answer?
Calendar duration is effort divided by effective capacity, plus a risk buffer. It applies the formula Weeks = effort hours ÷ (people × available hours) and shows the working so you can check each step by hand.
Is the Project Timeline Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.