What is an hours calculator?

An hours calculator lets you quickly and accurately measure how much time has passed based on the start and end times entered into the tool.

Calculating the time - like “How many hours am I working?” - isn’t as easy as it seems. An hour calculator can do it instantly with no hassle.

Our hours calculator accepts 12-hour and 24-hour formats. The tool can display the resulting time in:

• Hours and minutes
• Decimal hours
• Total number of minutes

The resulting elapsed times are often used in other calculations like:

• Total charges for labor, work, or billable hours
• Time clock, time card, and weekly timesheets
• Activity tracking/monitoring
• Time management

How to calculate elapsed time and time duration

Calculating elapsed time is easier with the 24-hour format, aka military time, and the format most Europeans use. If you’re using the 12-hour or standard time format to record start and end times, you’ll need to convert the recorded times to the 24-hour format.

To do this, add 12 hours to any time recorded during the PM period. Times recorded in the AM stay the same.

Example:

• 1:00 PM = 1:00 + 12:00 = 13:00
• 5:30 PM = 5:30 + 12:00 = 17:30
• 8:15 AM = 08:15

To get the time interval, subtract the start time from the end one. But we must calculate the difference between the hours and minutes separately.

Example:

First, convert the recorded times to the 24-hour format.

• Start Time: 8:15 AM = 08:15
• End Time: 5:30 PM = 17:30

Then subtract the start time from the end time. Do this separately for the hours and minutes.

• Elapsed minutes = 30 mins - 15 mins = 15 minutes
• Elapsed hours = 17 hours - 8 hours = 9 hours

Combine the resulting hours and minutes to get the total elapsed time.

• Elapsed time = 9:15 or 9 hours and 15 minutes

What if the end time minutes are smaller than the start time minutes?

We’ll get a negative result. This isn't a valid time or an accurate measure of the minutes component of the total interval/time duration.

Here's what to do:

• Remove 1 hour from the end time’s hours
• Convert that into minutes (which is 60)
• Add the extra 60 to the end time minutes

The total time elapsed remains the same. But we’ll end up with a positive number when we subtract the start time’s minutes.

Example:

• Start Time: 11:47 AM = 11:47
• End Time: 1:28 PM = 13:28

28 minutes - 47 minutes gives us -19 minutes which is not a valid time interval.

Subtract 1 hour from the end time’s hours. Add 60 minutes to the end time’s minutes.

• Converted end time hours = 13 hours - 1 hour = 12 hours
• Elapsed hours = 12 hours - 11 hours = 1 hour
• Converted end time minutes = 28 minutes + 60 minutes = 88 minutes
• Elapsed minutes = 88 minutes - 47 minutes = 41 minutes

Elapsed time = 1:41 or 1 hour and 41 minutes

Converting between digital time and decimal hours

To convert the digital time into decimal hours, divide the minutes by 60. The hours stay the same and don’t need any conversions.

Say you worked for 4 hours 45 minutes (4:45). Divide the 45 minutes by 60.

45 minutes ÷ 60 = 0.75 minutes

The hour number stays the same. So the decimal hour number for 4:45 or 4 hours 45 minutes = 4.75 hours.

Calculating decimal hours comes in handy for counting pay.

Converting elapsed time into minutes

Converting the elapsed time into a total number of minutes is easy. Multiply the elapsed hours by 60, then add the minutes to the resulting number.

• 4 hours 45 minutes
• 4 x 60 = 240 minutes
• 240 + 45 = 285 minutes

4 hours 45 minutes = 285 minutes