Online Timer
Product of Stuon
Time Duration Calculator
Enter a start and an end time to get the exact duration, even across midnight.
Add dates (optional, for multi-day spans)
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How to calculate a time duration
- Pick the start and end times.
- If the end is earlier than the start (say 10:00 PM to 6:00 AM), the calculator assumes it ends the next day.
- For spans longer than a day, open Add dates and fill in both dates.
The formula
Duration = end time − start time. If the result is negative, add 24 hours. To get decimal hours, divide the minutes by 60.
Example: 8:45 AM to 5:15 PM → 17:15 − 8:45 = 8:30 → 8 + 30/60 = 8.5 hours (510 minutes).
Frequently asked questions
How do I calculate time across midnight?
Add 24 hours to the end time before subtracting. 11:00 PM to 7:00 AM is (7:00 + 24:00) − 23:00 = 8 hours. The calculator does this automatically.
How do I convert a duration to decimal hours?
Divide the minutes by 60 and add them to the whole hours. 7 hours 45 minutes is 7 + 45/60 = 7.75 hours.
Does it account for daylight saving time?
When you add dates, the result uses real elapsed time on your device's clock, so a span that crosses a daylight saving change is an hour shorter or longer. Time-only calculations ignore DST.
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