How to calculate time in excel

Excel can work with time very easily.
Time can be entered in various different formats and calculations performed. There are one or two oddities, but nothing which should put you off working with it. See the TimeSheet example for an example.
When time is entered into worksheet it should be entered with a colon between the hour and the minutes, such as 12:30, rather than 12.30 

Typing time

When time is entered into worksheet it should be entered with a colon between
the hour and the minutes, such as 12:30, rather than 12.30s

Excel can cope with either the 24hour system or the am/pm system. To use the am/pm system you must enter the am or pm after the time. You must leave a space between the number and the text.

Finding the difference between two times

You can subtract two-time values to find the length of time between. If the result is not shown correctly, You may need to reformat the answer. Look at the section about formatting further in this worksheet.

Adding time

You can add time to find a total time. This works well until the total time goes above 24 hours. For totals greater than 24 hours you may need to apply some special formatting.

Formatting time

When time is added together the result may go beyond 24 hours. Usually, this gives an incorrect result, as in the example below. To correct this error, the result needs to be formatted with a Custom format.

How To Apply Custom Formatting

The custom format for time uses a pair of square brackets [hh] on either side of the hours' indicators.

1. Click on the cell which needs the format.
2. Choose the Format menu.
3. Choose Cells.
4. Click the Number tag at the top right.
5. Choose Custom.
6. Click inside the Type: box.
7. Type [hh]: mm as the format.
8. Click OK to confirm.