If you have to calculate hours based on 8:51 to 11:27 a.m. and then 12:32 to 5:15 p.m., it's going to take more work. Tip To calculate hours, add up the total hours and minutes worked.

How to Calculate an Employee's Time Card Using Military Time. Military time is confusing at first, but it makes a lot of sense to use it for calculations of time.

Setting up an Excel spreadsheet to calculate time worked. Follow these steps: In A1, enter Time In. In B1, enter Time Out. In C1, enter Hours Worked.