Calculating man hours involves determining how much time a project requires and how many employees are needed. The process can be completed before or after a project, and this example determines man hours after a project's completion. The calculations take a few minutes and require a calendar and a calculator.

**Calculate the project's timeframe**Use a calendar to determine when the project began and ended. Count how many work days the project ran, being careful to subtract holidays when employees were not working. For this example, assume the project ran for eight five-day weeks, for a total of 40 work days.

**Multiply days by hours**Determine how many hours your employees work each day, and do not count any unpaid time, such as lunch breaks. Assume that each employee works eight hours a day. Multiply the project's work days by a single employee's daily number of hours. In this example, 40 x 8 = 320. This is the number of hours a single employee spends on the project over the eight-week period.

**Multiply hours by employees**If more than one employee is assigned to the project, multiply the number of employees by the answer listed in the previous step. If one employee spends 320 hours on the project, and five employees are assigned to the task, 320 x 5 = 1,600. This is the total number of man hours performed on this project.