The Time Duration Calculator finds the exact amount of time between two times — in hours, minutes, and seconds. Whether you need to know how long a meeting lasted, how many hours you worked on a shift, how long a video or podcast runs, or how much time has passed between two events, this tool gives you an instant, precise answer.
Simply enter a start time and an end time — in 12-hour or 24-hour format — and the calculator will show the total duration broken down by hours, minutes, and seconds. It also handles times that cross midnight, so calculating the duration of an overnight shift from 11:00 PM to 7:00 AM works correctly. You can also add or subtract a time duration from a given start time to find when something ends.
This calculator is useful for timesheet calculations, sports timing, cooking, scheduling, billing hours for freelance work, and any situation where you need to know exactly how long something takes.
Time Duration Calculator
Add / Subtract Time from a Start
How the Time Duration Calculator Works
The calculator converts both times to total minutes since midnight, subtracts the start from the end to get the duration in minutes, then converts back to hours and minutes. If the “spans midnight” checkbox is checked (or the end time is earlier than the start time), it adds 24 hours to the result to handle overnight periods correctly. The add/subtract section adds or subtracts the given duration to a start time, wrapping around midnight using modulo arithmetic.
Example Calculations
Work shift: 9:15 AM to 5:45 PM = 8 hours 30 minutes (510 minutes). Overnight shift: 10:30 PM to 6:00 AM = 7 hours 30 minutes (450 minutes). Meeting: 2:00 PM to 3:45 PM = 1 hour 45 minutes. Add 2 hours 30 minutes to 11:15 PM = 1:45 AM (next day).
Decimal Hours Reference
| Minutes | Decimal Hours | Minutes | Decimal Hours |
|---|---|---|---|
| 15 | 0.25 | 45 | 0.75 |
| 20 | 0.33 | 50 | 0.83 |
| 30 | 0.50 | 10 | 0.17 |
Frequently Asked Questions
How do I calculate hours worked on a timesheet?
Enter your clock-in time as the start and your clock-out time as the end. If you took an unpaid break, calculate separately and subtract. For example, 8:00 AM to 5:00 PM with a 30-minute unpaid lunch = 9 hours − 0.5 hours = 8.5 hours worked.
Why do I need the “spans midnight” option?
Without it, the calculator would subtract a larger end-of-day number from a smaller one and get a negative result. The overnight option adds 24 hours to the duration so that a shift from 10 PM to 6 AM correctly shows 8 hours instead of a negative number.
How do I convert minutes to decimal hours?
Divide the minutes by 60. For example, 45 minutes = 45/60 = 0.75 hours. So 8 hours and 45 minutes = 8.75 hours. This decimal form is commonly used in timesheet software, payroll systems, and billing.
Can I calculate time in seconds?
This calculator works in hours and minutes, which covers most everyday uses. For seconds-level precision (timing races, lab experiments), multiply the total minutes by 60 and add any remaining seconds manually.
How do I add time to a clock time?
Use the “Add/Subtract Time” section at the bottom of the calculator. Enter your start time, add the hours and minutes you want to add, and the calculator will show you the resulting clock time — wrapping correctly past midnight if needed.