Time Calculator
Add and subtract any number of durations in hours, minutes and seconds, multiply or divide the total, and find the clock time after adding or taking away time.
Add and subtract durations
Formats: 1:30 (h:mm), 1:30:15 (h:mm:ss), 90m, 2h 15m, 1.5h, 45s, 1d 4h.
Clock time plus or minus a duration
How to use the Time Calculator
- Type a time in each row, such as 1:30:00, 45m or 2h 15m. Bare numbers are read as minutes unless you change the setting.
- Choose + or − for each row with the toggle button, and press Add row for more values.
- Read the total in HH:MM:SS, plus decimal hours, minutes, seconds and days.
- Multiply or divide the total, for example to find the time for 5 laps or an average per item.
- Use the clock section to add or subtract a duration from a time of day, such as 9:45 PM + 3h 30m.
How time arithmetic works
Time uses base 60 for minutes and seconds, so it can't be added like ordinary decimals. The reliable method is to convert everything to seconds, do the sum, and convert back:
- Convert each value: seconds = hours × 3600 + minutes × 60 + seconds.
- Add or subtract the totals.
- Convert back: hours = total ÷ 3600 (whole part), minutes = remainder ÷ 60, and what is left is seconds.
Example: 1:30:00 + 0:45:00 − 0:20:15. In seconds that is 5,400 + 2,700 − 1,215 = 6,885 seconds, which is 1 hour (3,600), 54 minutes (3,240) and 45 seconds: 01:54:45, or 1.9125 decimal hours.
Minutes to decimal hours
Timesheets and payroll often need hours as a decimal. Divide the minutes by 60:
| Minutes | Decimal hours | Minutes | Decimal hours |
|---|---|---|---|
| 5 | 0.0833 | 35 | 0.5833 |
| 10 | 0.1667 | 40 | 0.6667 |
| 15 | 0.25 | 45 | 0.75 |
| 20 | 0.3333 | 50 | 0.8333 |
| 25 | 0.4167 | 55 | 0.9167 |
| 30 | 0.5 | 60 | 1.0 |
A common mistake is to read 7:30 as 7.3 hours. It is really 7.5 hours, because 30 minutes is half an hour.
Adding time to a clock across midnight
When you add a duration to a time of day, anything past 24 hours rolls over into the next day. 9:45 PM is 21:45 on a 24-hour clock; adding 3 hours 30 minutes gives 25:15, which is 1:15 AM the next day. Subtracting works the same way in reverse: 1:00 AM minus 2 hours is 11:00 PM on the previous day. The calculator shows the day change for you, including multi-day durations such as 50 hours.
For working out the time between two clock times, such as a shift from 10:30 PM to 6:15 AM, the hours calculator and time duration calculator are quicker.
Useful time conversions
| Unit | Seconds | Minutes | Hours |
|---|---|---|---|
| 1 minute | 60 | 1 | 0.0167 |
| 1 hour | 3,600 | 60 | 1 |
| 1 day | 86,400 | 1,440 | 24 |
| 1 week | 604,800 | 10,080 | 168 |
Frequently asked questions
How do I add hours and minutes?
Add the minutes together and the hours together. If the minutes come to 60 or more, carry each full 60 minutes into the hours. For 2:45 + 1:30, the minutes are 45 + 30 = 75, which is 1 hour 15 minutes, so the total is 4:15.
How do I convert minutes to decimal hours?
Divide the minutes by 60. 15 minutes is 0.25 hours, 30 minutes is 0.5, and 45 minutes is 0.75, so 7 hours 45 minutes is 7.75 hours. This is the format most payroll and timesheet systems use.
What does 1:30 mean in this calculator?
Two numbers separated by a colon are read as hours and minutes, so 1:30 is 1 hour 30 minutes. Three numbers, like 1:30:15, are hours, minutes and seconds, and four numbers add days in front. To enter minutes and seconds, write 0:01:30 or 1m 30s.
How do I subtract one time from another?
Turn both into seconds (or minutes), subtract, and convert back. In the calculator, enter the first time with + and the second with −. If the second time is larger, the result is shown as a negative duration, for example −00:15:00.
What time is it 8 hours from now?
Enter the current time in the clock section, choose plus and type 8h. The calculator shows the new time and tells you if it falls on the next day. For example 9:45 PM + 8 hours is 5:45 AM the next day.
How many seconds are in a day?
There are 86,400 seconds in a day (24 x 60 x 60), 1,440 minutes in a day and 168 hours in a week.