⏱️ Time Duration Calculator
Work out how long it is from one clock time to another, including overnight spans, in hours and minutes or decimal hours.
Quick answer: Subtract the start time from the end time. From 9:15 AM to 5:45 PM is 8 hours 30 minutes – 8.5 decimal hours or 510 minutes – and 10:00 PM to 6:30 AM the next morning is 8 hours 30 minutes too.
Updated · Free · No sign-up · Works on any device
Time Duration Calculator inputs
Result
9:15 AM to 5:45 PM
8 h 30 min
| Hours and minutes | 8:30 |
| Decimal hours | 8.5 |
| Total minutes | 510 |
- Total seconds
- 30,600
- Share of a day
- 35.42%
- Crosses midnight
- No
Same start, other end times
| End time | Duration | Decimal hours |
|---|---|---|
| 10:15 AM | 1 h | 1 |
| 11:15 AM | 2 h | 2 |
| 1:15 PM | 4 h | 4 |
| 3:15 PM | 6 h | 6 |
| 5:15 PM | 8 h | 8 |
| 7:15 PM | 10 h | 10 |
| 9:15 PM | 12 h | 12 |
How to calculate the time between two times
Convert both times to minutes after midnight (hours × 60 + minutes), subtract, and convert back. If the result is negative the period crosses midnight, so add a full day of 1,440 minutes.
Duration (min) = (end − start + 1,440) mod 1,440 · Decimal hours = minutes ÷ 60
Worked examples
9:15 AM to 5:45 PM: 9:15 is 555 minutes after midnight and 17:45 is 1,065. The difference is 510 minutes = 8 hours 30 minutes = 8.5 hours.
10:00 PM to 6:30 AM: 390 − 1,320 = −930, plus 1,440 gives 510 minutes – also 8 h 30 min, with the end on the next day.
Minutes to decimal hours
| Minutes | Decimal | Minutes | Decimal |
|---|---|---|---|
| 6 | 0.10 | 30 | 0.50 |
| 10 | 0.17 | 40 | 0.67 |
| 15 | 0.25 | 45 | 0.75 |
| 20 | 0.33 | 50 | 0.83 |
Using 24-hour time
Subtraction is easiest on the 24-hour clock, where 1:00 PM is 13:00 and 11:30 PM is 23:30. Convert both times first, subtract the hours and minutes separately, and borrow 60 minutes from the hours whenever the end minutes are smaller than the start minutes. For example, 14:10 − 9:45 becomes 13:70 − 9:45 = 4 hours 25 minutes. The calculator does this borrowing for you and also handles the jump past midnight.
Tips
- Shift work: for several shifts with breaks and pay, use the hours calculator time card.
- AM/PM mistakes are the most common error – 12:00 AM is midnight and 12:00 PM is noon.
- Billing: many timesheets round to the nearest 6 or 15 minutes; round the minutes before converting to decimal.
Frequently asked questions
How do I calculate time across midnight?
If the end time is earlier than the start time, add 24 hours to the end before subtracting. 10:00 PM (22:00) to 6:30 AM becomes 30:30 − 22:00 = 8 hours 30 minutes. The calculator does this automatically.
How do I convert minutes to decimal hours?
Divide the minutes by 60. 30 minutes is 0.5 hours, 15 minutes is 0.25 and 45 minutes is 0.75, so 8 h 45 min is 8.75 hours.
Can it handle durations longer than 24 hours?
Two clock times can only be up to 23 h 59 min apart. For longer spans across several days use the date difference calculator, or add whole days of 24 hours yourself.
Should I enter times in 12-hour or 24-hour format?
The time picker follows your device settings; either way the time is stored in 24-hour form, so 5:45 PM is 17:45. Results show both the 12-hour clock and decimal hours.