Add or subtract hours, minutes and seconds, total a list of durations, or find the time a given number of hours and minutes before or after a clock time.
How to add and subtract time
Time uses base 60: 60 seconds in a minute and 60 minutes in an hour. To add times by hand, add each unit separately, then carry over every 60 seconds into a minute and every 60 minutes into an hour.
Worked example
2 h 45 m + 1 h 30 m 30 s − 20 m:
- Hours: 2 + 1 = 3
- Minutes: 45 + 30 − 20 = 55
- Seconds: 30
Total: 3 h 55 m 30 s, or 3.925 decimal hours. Starting at 9:15 AM, that ends at 1:10 PM (ignoring the seconds).
Converting time to decimal hours
Decimal hours = hours + minutes ÷ 60 + seconds ÷ 3,600
Decimal hours are useful for timesheets and billing: 3 h 55 m is 3.92 hours, not 3.55.
Frequently asked questions
Can the result be negative?
Yes, if you subtract more time than you add. The result is shown with a minus sign.
What happens if the clock time passes midnight?
The calculator shows the new time and notes that it falls on the next (or previous) day.
Related tools
Results are estimates for planning and education only. They are not financial, tax, legal or medical advice. Check important numbers with a qualified professional.