About time durations
This calculator adds or subtracts two durations given in hours, minutes and seconds, and can also add a duration to a start time to find the end time, rolling over correctly past midnight. It runs in your browser; nothing is uploaded.
How Time Duration works
How it works
Each duration is converted to total seconds, combined, then converted back into hours, minutes and seconds. For the "add to a time" mode, the start clock time is turned into seconds since midnight, the duration is added or subtracted, and the result wraps around a 24-hour day, reporting any day change.
Worked example
2 h 30 m plus 1 h 45 m = 4 h 15 m (9,000 s + 6,300 s = 15,300 s). Starting at 22:00 and adding 5 h 30 m gives 03:30 the next day.
Common uses
- Add two time durations
- Subtract one duration from another
- Add hours and minutes to a time
- Find an end time from a start time
- Total lap or session times
- Work out time across midnight
- Sum hours worked
- Convert a duration to seconds
Frequently asked questions
How do I add two durations?
Enter each in hours, minutes and seconds, choose +, and the total appears instantly.
Can it subtract times?
Yes — choose the minus option; negative results are shown with a minus sign.
Does it handle crossing midnight?
Yes — the "add to a time" mode wraps past 24:00 and tells you how many days were added.
Can I get the total in seconds?
Yes — the result also shows the total in seconds and minutes.
Is my data uploaded?
No — it is all calculated in your browser.
Is it free?
Yes, completely free.