Explanation

In the Excel date system, one day is equal to 1, so you can think of time as fractional values of 1, as shown in the table below:

HoursFractionMinutesSecondsValueTime
11/246036000.041671:00
33/24180108000.1253:00
66/24360216000.256:00
1212/24720432000.512:00
1818/241080648000.7518:00
2424/241440864001.021:00

Since there are 24 hours in a day, 60 minutes in each hour, and 60 seconds in each minute, you need to divide by 24 * 60 * 60 = 86400 in order to convert decimal seconds to a value that Excel will recognize as time. After dividing by 86400, you can apply a time format of your choice, or use the result in a math operation with other dates or times.

In the example, since B11 contains 43200 (representing 43200 seconds, or a half day) the result is 43200/86400 = 0.5. Once a time format like h:mm or [h]:mm is applied, Excel will display 12:00.

Displaying a time duration

To display hours that represent a duration longer than 24 hours, minutes in durations longer than 60 minutes, or seconds in durations over 60 seconds, you’ll need to adjust the number format by adding square brackets.

[h]  // for hours greater than 24
[m]  // for minutes greater than 60
[s]  // for seconds greater than 60

The brackets tell to Excel the time is a duration, and not a time of day.

Note: to use square brackets, you’ll need to create and apply a custom number format . Select cells, then go to Format Cells (Control + 1) > Number > Custom.

Explanation

In the Excel time system, one 24-hour day is equal to 1. This means times and hours are fractional values of 1, as shown in the table below:

HoursTimeFractionValue
11:00 AM1/240.04167
33:00 AM3/240.125
66:00 AM6/240.25
44:00 AM4/240.167
88:00 AM8/240.333
1212:00 PM12/240.5
186:00 PM18/240.75
219:00 PM21/240.875

Because each hour can be represented as 1/24, you can convert an Excel time into decimal hours by multiplying the value by 24. For example, with the time value 6:00 cell A1, you can visualize the conversion like this:

=A1*24
=(6/24)*24
=0.25*24
=6

Format result as number

When you multiply a time value by 24, Excel may automatically format the result using a time format like h:mm, which will display the value incorrectly. To display the result as a regular number, apply the General or Number format .