In short: A time duration is the end time minus the start time: from 9:15 AM to 5:45 PM is 8 hours 30 minutes, or 8.5 decimal hours. If the end time is earlier, the duration runs past midnight. To add durations, add the seconds, minutes and hours in their own columns and carry every 60. The calculator does both and takes off a break.
How to calculate time duration between two times
- Write both times on the 24-hour clock. 9:15 AM stays 9:15; 5:45 PM becomes 17:45, because PM hours other than 12 gain 12.
- Subtract the start from the end, hours from hours and minutes from minutes. 17:45 minus 9:15 is 8 hours and 30 minutes. If the minutes come out negative, borrow an hour: 17:15 minus 9:45 is 8 hours minus 30 minutes, which is 7 hours 30 minutes.
- Take off any unpaid break. The same day with a 45 minute lunch is 7 hours 45 minutes, or 7.75 hours.
- Read it the way you need it. 8:30:00 on the clock, 8 hours 30 minutes in words, 8.5 in decimal hours, or 510 minutes.
Working in minutes after midnight is the same sum with one less step: 9:15 is 555 minutes, 17:45 is 1,065, and the difference is 510 minutes. Every result here is worked out in whole seconds in your browser, so the hours and minutes, the decimal hours and the minutes always describe exactly the same span.
Time duration past midnight
When the end time is earlier than the start time, the span crosses midnight and the calculator adds 24 hours before subtracting. A night shift from 22:30 to 6:15 is 6:15 plus 24 hours, that is 30:15, minus 22:30, which gives 7 hours 45 minutes (7.75 hours). The result says when it has crossed midnight, so you can check that the overnight reading was what you meant. Two identical times give 0, because a span of exactly 24 hours and no time at all look the same on a clock; enter a 24 hour shift as two parts and add them in the second box.
Adding and subtracting hours, minutes and seconds
Clock arithmetic is ordinary addition with a carry of 60 instead of 10. To add 1:45, 2:30, 0:50, add the minutes first: 45 plus 30 plus 50 is 125, which is 2 hours and 5 minutes. Then add the hours, 1 plus 2 plus 0 plus the 2 carried, for 5:05, or 5.08 decimal hours. Seconds work the same way one column further right: 0:48:30 plus 0:36:45 plus 1:05:50 is 2:31:05. Subtraction borrows the other way: 8:00 -0:30 -0:15 leaves 7:15, the length of an eight hour day after two short breaks. Type one duration per line, in whichever form you have it, and put a minus sign in front of anything to take away. A line the calculator cannot read is listed under the result rather than silently dropped.
Hours and minutes as decimal hours
Timesheets, invoices and payroll multiply hours by a rate, so they want decimal hours: the minutes divided by 60. Fifteen minutes is 0.25, twenty minutes is 0.33 and forty-five minutes is 0.75. The table gives the durations people convert most, with the clock form, the words, the decimal hours, the minutes and the seconds side by side. For every minute from 1 to 60, including the tenth and quarter hour rounding some payroll systems use, see the minutes to decimal hours chart.
| Clock | In words | Decimal hours | Minutes | Seconds |
|---|---|---|---|---|
| 0:15 | 15 minutes | 0.25 | 15 | 900 |
| 0:20 | 20 minutes | 0.33 | 20 | 1,200 |
| 0:30 | 30 minutes | 0.5 | 30 | 1,800 |
| 0:40 | 40 minutes | 0.67 | 40 | 2,400 |
| 0:45 | 45 minutes | 0.75 | 45 | 2,700 |
| 0:50 | 50 minutes | 0.83 | 50 | 3,000 |
| 1:15 | 1 hour 15 minutes | 1.25 | 75 | 4,500 |
| 1:30 | 1 hour 30 minutes | 1.5 | 90 | 5,400 |
| 2:30 | 2 hours 30 minutes | 2.5 | 150 | 9,000 |
| 7:30 | 7 hours 30 minutes | 7.5 | 450 | 27,000 |
| 8:00 | 8 hours | 8 | 480 | 28,800 |
| 8:30 | 8 hours 30 minutes | 8.5 | 510 | 30,600 |
| 8:45 | 8 hours 45 minutes | 8.75 | 525 | 31,500 |
| 10:00 | 10 hours | 10 | 600 | 36,000 |
Breaks, lunch and hours on the clock
An unpaid lunch comes off the duration, a paid break does not. Put the unpaid minutes in the break box and the calculator subtracts them from the span between clocking in and clocking out, so 9:15 AM to 5:45 PM with 45 minutes for lunch is 7 hours 45 minutes on the clock. For a whole week of start and finish times with overtime and gross pay, use the work hours calculator; for how a time card total such as 38:45 becomes 38.75 hours, read how to calculate hours worked. Rotas and timesheets that give times as 1730 or 2200 are using military time, which this calculator reads directly; the military time converter explains the form and how each time is said.
Time duration between two dates
This page works on clock times within a day, or across one midnight. For a span of days, weeks or months, the days between dates calculator counts the calendar days between two dates, with or without the end date, and the business days calculator counts working days only. To find the hours a meeting falls at in another city, the time zone meeting planner lines up the working day of up to four places.
Questions people ask
How do you calculate the time duration between two times?
Turn both times into minutes after midnight and subtract the start from the end. 9:15 AM is 555 minutes and 5:45 PM is 1,065, so the difference is 510 minutes, which is 8 hours 30 minutes or 8.5 decimal hours. The calculator does this for you and also takes off any unpaid break you enter.
What if the end time is earlier than the start time?
Then the duration runs past midnight into the next day, and the calculator adds 24 hours before subtracting. 22:30 to 6:15 is 7 hours 45 minutes. It tells you when a result crosses midnight. If the two times are the same, the duration is 0; enter the shift as two parts if it really is 24 hours.
How do I add hours, minutes and seconds?
Add the seconds, the minutes and the hours in separate columns, then carry: every 60 seconds becomes a minute and every 60 minutes becomes an hour. 1:45 plus 2:30 plus 0:50 is 3 hours and 125 minutes, and 125 minutes is 2 hours 5 minutes, so the total is 5:05. Type one duration per line and the calculator adds them, with a minus sign to subtract a line.
How do I convert a duration to decimal hours?
Divide the minutes by 60 and add the hours. 8 hours 30 minutes is 8.5 hours, 7 hours 20 minutes is 7.33 and 45 minutes is 0.75. The calculator shows decimal hours next to every result, because timesheets and payroll multiply decimal hours by a rate.
Can I enter 12-hour times with AM and PM?
Yes. Type 9:15 AM, 5:45pm, 9 am, noon or midnight. A time without AM or PM is read on the 24-hour clock, so 17:30 is half past five in the afternoon and 1730 means the same. Seconds are accepted too, as in 9:15:30.
Does it count the time between two dates?
No, this page works on clock times within a day or across one midnight. For the days between two dates use the days between dates calculator, and for working days only, the business days calculator.
Are the times I type sent anywhere?
No. The calculation runs in your browser. A share link carries your times in the part after the # in the address, which browsers never send to a server.