Excel can perform calculations with time values entered in various formats. It can subtract times to find durations, and add times to get totals, though totals over 24 hours may require custom formatting. To correctly format times totaling over 24 hours, apply the custom format [hh]:mm to the cell, which will display the hours within square brackets.

1. Excel Function Dictionary Time Calculation
© 1998 - 2000 Peter Noneley Page 1 of 2
A B C D E F G H I J
1 Time Calculation
2
3 Excel can work with time very easily.
4 Time can be entered in various different formats and calculations performed.
5 There are one or two oddities, but nothing which should put you off working with it.
6 See the TimeSheet example for an example.
7
8 Typing time
9 When time is entered into worksheet it should be entered with a colon between
10 the hour and the minutes, such as 12:30, rather than 12.30
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12 1:30 12:30 20:15 22:45
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14 Excel can cope with either the 24hour system or the am/pm system.
15 To use the am/pm system you must enter the am or pm after the time.
16 You must leave a space between the number and the text.
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18 1:30 AM 1:30 PM 10:15 AM 10:15 PM
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20 Finding the difference between two times
21 You can subtract two time values to find the length of time between.
22
23 Start End Duration
24 1:30 2:30 1:00 =D24-C24
25 8:00 17:00 9:00 =D25-C25
26 8:00 AM 5:00 PM 9:00 AM If the result is not shown correctly,
27 You may need to reformat the answer.
28 Look at the section about formatting
29 further in this worksheet.
30
31 Adding time
32 You can add time to find a total time.
33 This works well until the total time goes above 24 hours.
34 For totals greater than 24 hours you may need to apply some special formatting.
35
36 Start End Duration
37 1:30 2:30 1:00
38 8:00 17:00 9:00
39 7:30 AM 5:45 PM 10:15
40 20:15
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42 Formatting time
43 When time is added together the result may go beyond 24 hours.
44 Usually this gives an incorrect result, as in the example below.
45 To correct this error, the result needs to be formatted with a Custom format.
46
47 Example 1 : Incorrect formatting
48 Start End Duration
49 7:00 18:30 11:30
50 8:00 17:00 9:00
51 7:30 17:45 10:15
52 Total 6:45 =SUM(E49:E51)
53
54 Example 2 : Correct formatting
55 Start End Duration
56 7:00 18:30 11:30
57 8:00 17:00 9:00
58 7:30 17:45 10:15
59 Total 30:45 =SUM(E56:E58)
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61

2. Excel Function Dictionary Time Calculation
© 1998 - 2000 Peter Noneley Page 2 of 2
A B C D E F G H I J
62 How To Apply Custom Formatting
63 The custom format for time use a pair of square brackets [hh] on either side
64 of the hours indicators.
65
66 1. Click on the cell which needs the format.
67 2. Choose the Format menu.
68 3. Choose Cells.
69 4. Click the Number tag at the top right.
70 5. Choose Custom.
71 6. Click inside the Type: box.
72 7. Type [hh]:mm as the format.
73 8. Click OK to confirm.
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