How to use the crew hours and duration calculator
- Enter the total person hours for the job. Two people working 3 hours is 6 person hours.
- Choose Time for a crew to see how long a crew of a given size takes, or Crew for a deadline to see how many workers you need.
- Enter the crew size or the days available, and the hours each person works per day.
- Optionally enter workdays per week to turn days into calendar weeks.
Formula
Hours per worker = total person hours / crew size
Working days = hours per worker / hours per day
Crew needed = total person hours / (days available x hours per day), rounded up to a whole person
Days with that crew = total person hours / (crew x hours per day)
Crews are whole people, so the crew size for a deadline is rounded up and the days with that crew can be shorter than the deadline.
240 person hours with a crew of 3
A job that takes 240 person hours, done by 3 workers, takes 80 hours each. At 8 hours a day that is 10 working days. With a crew of 7, each person works 34.29 hours, which is 4.29 days, so you would schedule 5 whole days, or 0.86 of a five day week.
For the reverse question, finishing the same 240 person hours in 10 days at 8 hours a day needs exactly 3 workers. In 7 days it needs 240 / 56 = 4.29, rounded up to 5 workers, who then finish in 6 days.
Person hours
Person hours measure the amount of work as if one person did it all. Dividing by the number of workers shows how the work spreads out, while dividing by the hours in a day shows how many days it covers. The same job can be done by a few people over many days or by many people over a few.
Your estimate of the total person hours is the key input. If you are unsure, estimate best, likely and worst cases with the three point estimate calculator.
Why real crews differ from the math
The arithmetic assumes every person works at the same pace and that the work can be shared evenly. In practice, adding people can add coordination time, tasks can depend on each other, and weather, deliveries and inspections can pause work. None of that is modeled here.
To put a cost on the hours, use the labor cost calculator. To compare overtime for existing staff with hiring, see the overtime vs new hire calculator, and to price a job for a client use the project quote calculator.
Assumptions and limits
- Everyone works the same number of hours at the same pace.
- The work can be divided evenly among the crew.
- Delays, setup time and coordination costs are not included.
- The crew for a deadline is rounded up to whole people.
Frequently asked questions
How many days will a job take with a crew?
Divide the total person hours by the crew size, then by the hours each person works per day. 240 person hours, 3 workers and 8 hour days is 10 days.
What are person hours?
The total work expressed as hours for one person. A job of 240 person hours takes one person 240 hours or three people 80 hours each.
How do I find the crew size for a deadline?
Divide the person hours by the days available and the hours per day, then round up to a whole person. The tool also shows how many days that crew would take.
Will doubling the crew halve the time?
In the arithmetic yes, but real jobs often do not scale that cleanly because of coordination and dependencies. Treat the result as a best case.