How to calculate Man hours in 3 simple steps

how to calculate Man-hour
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How to calculate Man hours

Man hours is the total hour worked over a specific period of time. As a health and safety personnel you need to understand how to calculate man-hour since it is necessary for determining the health and Safety performance.

Man-hours are a crucial element in submitting a winning project bid as well as charging for work completed. Because labor constitutes such a large portion of any contract work, estimating and reporting hours accurately is crucial to having a successful business.


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How to calculate man hours formula =

Total hours work a day x Total number of workers x Total numbers of days worked over the specific period of time


Consider that:

  • Number of hours worked a day: 8 hours
  • Total number of workers: 20 workers
  • Specific period of time: 3 months – 90 days (January – March), minus weekends and public holidays.

Assuming that weekend and public holidays = 24 days

We subtract 24 from the number of days within the 3 months

90 – 24 = 66 days


Man-hour = 8 x 20 x 66

= 10,560 hours.

From the example above, man-hour is calculated from simple parameter.

You can substitute the values with your organization’s specific value to determine the man-hour for a specific period for your organization.

Note that: Man-hour is an integral factor in measuring Health and safety performance.

An organization that records 5 LTI in every 10,000 man-hour every 3 months and the organization that record 10 LTI in every 100,000 man-hour every 3 month poses different Health and safety performance level. Judging by the man-hour and the LTI recorded, the second organization has a better Health and Safety performance.

This is the essence of knowing the man-hour.

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  1. Does not account for vacations, 10 holiday days and medical leave of the people and and a variable needs to be considered. Man year starts at 2080 – estimated vacation – estimated sick leave – holidays. I like to use 1950 as my man year in hours. Also need to assume they are working one project if not you will need to account for that. IMO

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