Job Duration Calculator Formula
Understand the math behind the job duration calculator. Each variable explained with a worked example.
Formulas Used
Working Days Needed
days_needed = (workers * hours_per_day) > 0 ? ceil(total_work_hours / (workers * hours_per_day)) : 0Weeks Needed (5-day weeks)
weeks_needed = (workers * hours_per_day) > 0 ? ceil(total_work_hours / (workers * hours_per_day)) / 5 : 0Hours Per Worker
hours_per_worker = workers > 0 ? total_work_hours / workers : 0Variables
| Variable | Description | Default |
|---|---|---|
total_work_hours | Total Work Hours Needed(hours) | 200 |
workers | Number of Workers | 4 |
hours_per_day | Hours Per Day(hours) | 8 |
How It Works
How to Calculate Job Duration
Formula
Days Needed = Total Work Hours / (Number of Workers x Hours Per Day)
This gives you the minimum calendar days required. In practice, add buffer time for weather delays, material availability, inspections, and other interruptions.
Worked Example
A project requires 200 work-hours with 4 workers working 8 hours per day.
- 01Daily crew output = 4 workers x 8 hours = 32 hours/day
- 02Days needed = 200 / 32 = 6.25, rounded up to 7 days
- 03Weeks needed = 7 / 5 = 1.4 weeks
- 04Hours per worker = 200 / 4 = 50 hours
Frequently Asked Questions
How do I account for delays?
Add a buffer of 10-20% to your estimated days. For outdoor projects, add more for weather delays. For complex projects, consider dependencies between tasks that may prevent parallel work.
Does adding workers always reduce duration?
Not always proportionally. Adding workers increases coordination overhead. There is also a physical limit to how many workers can operate in a space. Beyond a certain point, more workers can actually slow things down.
Ready to run the numbers?
Open Job Duration Calculator