Man Month calculation - how many man days or man hours ?

Hello,

How can I calculate how many man days or man hours are in one man month ?

The first option how to calculate the number of man hours in one man month, is to use an exact number of man days in a specific month. For example August 2021 has 22 business days. One man day is equal to 8 man hours, so the calculation will be 22 x 8 = 176 man hours.

The second option is to use 160 man hours for every month. This method is universal, because it uses 40 hours per week and 4 weeks per each month. It is not absolutely accurate, because some months have more than 20 working days. But on the other side, employees usually don't work on every business day, because they are sometimes on vacation, having bank holidays, national holidays or other days off during a year.

To calculate the number of man hours in a month, you can also use a method, that is based on 40 hours per week and 52 weeks per year, because 1 year has approx. 52 weeks.

First, get the number of total man hours per year:

40 x 52 = 2080 man hours

Then calculate the number of man days in a month:

2080 / 12 = 173.33 man hours

To make it more simple, instead of using 173.33 man hours, there are often used only 173 man hours per month.