How to use the time calculator
Pick one of three jobs at the top of the form. The answer updates as you type.
- Add or subtract: enter each time as hours, minutes and seconds, one per row, and set a row to - Subtract to take it away. Add a time adds rows. Use it as a time duration calculator for laps, tasks or video clips.
- Multiply or divide: enter one time and a number, for example a 45-minute class times 12, or a 7:30:00 shift divided by 4.
- Clock time: enter a start time and the hours and minutes to add or take away, for example 9:45 AM plus 3 hours 30 minutes. The result says if it falls on the next day or an earlier one.
Entries need no tidying: 90 minutes, 125 seconds or 1.5 hours all work. The result is shown as h:mm:ss, in words, as decimal hours, and as total minutes and seconds. A negative total, where you took away more than you added, has a minus sign and a note.
This page does not work out the time between two clock times. For that, use the hours calculator, and for a week of start and end times with overtime, the time card calculator.
How to add hours and minutes by hand
Hours and minutes do not add like ordinary decimals, because an hour has 60 minutes, not 100. The method is:
- Add the hours, the minutes and the seconds in separate columns.
- If the seconds come to 60 or more, take away 60 and carry 1 minute.
- If the minutes come to 60 or more, take away 60 and carry 1 hour.
Adding 2 h 45 min, 1 h 30 min and 3 h 50 min:
| Step | Hours | Minutes |
|---|---|---|
| Add each column | 6 | 125 |
| 125 minutes is 2 hours and 5 minutes, so carry 2 | 6 + 2 | 5 |
| Total | 8 | 5 |
So the total is 8 hours 5 minutes, or 8:05. The same carrying works as a time calculator for minutes and seconds: 4 min 35 s plus 3 min 50 s is 7 min 85 s, and 85 seconds is 1 minute 25 seconds, so the answer is 8 min 25 s.
To subtract, borrow instead of carrying. For 5 h 10 min minus 2 h 45 min, 45 minutes cannot come out of 10, so turn 1 of the 5 hours into 60 minutes: 4 h 70 min minus 2 h 45 min is 2 h 25 min.
For long lists, turn every time into seconds (hours x 3,600 + minutes x 60 + seconds), add or subtract, then turn the answer back. That is what the calculator does.
Multiplying and dividing a time
To multiply or divide a time by a number, turn it into seconds, do the sum, and turn the answer back into hours, minutes and seconds. For 1:45:30 x 4: 1:45:30 is 6,330 seconds, times 4 is 25,320 seconds, which is 7 hours, 2 minutes and 0 seconds.
| Example | Sum | Answer |
|---|---|---|
| A 1:45:30 lap, 4 laps | 1:45:30 x 4 | 7:02:00 |
| A 45-minute class, 12 classes | 0:45:00 x 12 | 9:00:00 |
| A 7:30:00 shift split 4 ways | 7:30:00 / 4 | 1:52:30 |
| 2 hours shared by 3 people | 2:00:00 / 3 | 0:40:00 |
| A 3:30:00 marathon, per mile (26.2) | 3:30:00 / 26.2 | 0:08:01 |
| The same marathon, per km (42.195) | 3:30:00 / 42.195 | 0:04:59 |
Division often gives part of a second, so the calculator rounds to the nearest whole second. The marathon pace is 480.9 seconds a mile, shown as 0:08:01, and 298.6 seconds a kilometer, shown as 0:04:59. You cannot divide by zero; the form says so if you try.
Adding time to a clock time
Adding to a time of day works the same way, but the clock starts again at midnight, and each time the total passes midnight the result moves to the next day.
| Start | Add or subtract | Result |
|---|---|---|
| 9:45 AM | + 3 h 30 min | 1:15 PM, same day |
| 10:30 PM | + 5 h 45 min | 4:15 AM, next day |
| 8:00 AM | - 9 h 30 min | 10:30 PM, previous day |
| 6:00 PM | + 50 h | 8:00 PM, 2 days later |
For 9:45 AM plus 3 h 30 min: 45 + 30 minutes is 75 minutes, which is 1 hour 15 minutes, and 9 + 3 + 1 is 13 hours, which is 1 PM on a 12-hour clock. The result also shows the 24-hour time, here 13:15. To change between the two styles, see the military time converter.
Time calculator in Excel or Google Sheets
Excel and Google Sheets store a time as part of a day. Microsoft explains that "12:00 PM is represented as 0.5 because it is half of a day", and Google's format guide says the part after the decimal point "counts the time as a fraction of one day". That is why a total of 28 hours can show up as 4:00: a normal time format only shows the clock time inside one day.
Enter each duration as h:mm:ss, for example 12:45:00, in cells A2 to A6. Then:
| To get | Formula | Format the answer as |
|---|---|---|
| Total of the list | =SUM(A2:A6) | [h]:mm:ss |
| One time minus another | =A2-A3 | [h]:mm:ss |
| A time times 4 | =A2*4 | [h]:mm:ss |
| A time divided by 4 | =A2/4 | [h]:mm:ss |
| Decimal hours of a total in A7 | =A7*24 | Number |
| Total minutes | =A7*1440 | Number |
| Total seconds | =A7*86400 | Number |
The square brackets around h are what stop the hours going back to 0 after 24. In Excel, choose Format Cells, then Custom, and type a format such as Microsoft's own [h]:mm;@; Microsoft says to "Take note of the colon after [h] and a semicolon after mm". With it, Microsoft's example of 12:45 plus 15:30 shows as 28 hours and 15 minutes. In Google Sheets, use Format, Number, Custom number format; Google's format reference lists the bracketed hour code as the "Number of elapsed hours in a time duration".
To add time to a clock time in B2, =B2+TIME(3,30,0) adds 3 hours 30 minutes. TIME cannot add a day or more, because Microsoft notes that for hours "Any value greater than 23 will be divided by 24 and the remainder will be treated as the hour value". For 50 hours, use =B2+50/24. More on decimal hours is on the time to decimal page.
Questions and answers
How do I add hours and minutes together?
Add the hours and the minutes separately, then turn every 60 minutes into an hour. 2 h 45 min plus 1 h 30 min is 3 h 75 min, which is 4 h 15 min.
How do I subtract one time from another?
Choose Add or subtract, enter the first time, then set the second row to Subtract. By hand, borrow 60 minutes from the hours when you need to: 5 h 10 min minus 2 h 45 min is 2 h 25 min.
How do I multiply a time by a number?
Turn the time into seconds, multiply, and turn it back. A 45-minute class 12 times is 540 minutes, which is 9 hours. Choose Multiply or divide on the form to do it in one step.
What time will it be 8 hours from now?
Choose Clock time, enter the time now and 8 hours. From 9:45 PM, 8 hours later is 5:45 AM the next day.
Why does my spreadsheet show 4:15 instead of 28:15?
The cell has a clock-time format, which starts again at 0 after 24 hours. Format the total as [h]:mm (Excel) or with a custom [h]:mm:ss format (Google Sheets) to show all the hours.
Can the result be negative?
Yes. If you take away more time than you add, the total is shown with a minus sign, such as -1:15:00, with a note under it. A negative result is often a sign that a row was set to Subtract by mistake.
Sources
Checked on 9 October 2026. If a rule has changed, please tell us.