Hours to days converter

How hours are converted to days

There are two kinds of day in this conversion. A workday is the number of hours you work in a day, so workdays = hours ÷ workday length. A calendar day is always 24 hours, so calendar days = hours ÷ 24. Work weeks are workdays divided by the number of workdays in your week, and a full-time work month is the hours in a working year spread over 12 months: workday length × days per week × 52 ÷ 12, which is about 173.3 hours for a standard 40-hour week.

Worked example: a project estimated at 100 hours, with 8-hour workdays, takes 100 ÷ 8 = 12.5 workdays, which is 2.5 five-day work weeks or 0.58 of a work month. Measured in round-the-clock time, the same 100 hours are 100 ÷ 24 = 4.17 calendar days, or 4 days and 4 hours.

2,080 hours is the figure many US employers use for a full-time year: 40 hours × 52 weeks, before holidays and vacation.

Choosing the right kind of day

Use workdays when the hours are labour: an estimate for a task, overtime to take back as time off, or annual leave given in hours. Use calendar days for anything that runs continuously, such as a machine running time, a rental period, a flight or the age of a newborn in hours. Mixing them up is the classic mistake: 72 hours of work is nine 8-hour workdays, but 72 hours of elapsed time is just three days.

Remember that a workday on paper is not the same as focused time. Meetings, email and interruptions often take a large part of an 8-hour day, so when you convert a task estimate into a delivery date, a planning figure of 5 or 6 productive hours per day usually gives a more realistic schedule. The table under the result shows how much the answer moves with different workday lengths.