How do I calculate the duration between two times?

Subtract the start time from the end time in total minutes. For example, from 9:15 AM to 5:45 PM: convert both to minutes since midnight (9:15 = 555 minutes; 5:45 PM = 17:45 = 1065 minutes), then subtract (1065 - 555 = 510 minutes = 8 hours 30 minutes). If the end time is earlier than the start time, add 1,440 minutes (24 hours) to account for an overnight span.

What if the end time is before the start time?

When the end time is earlier than the start time, the duration spans midnight. The calculator automatically adds 24 hours to the result so you get the correct overnight duration. For example, from 10:00 PM to 6:00 AM is 8 hours, not a negative value.

How do I convert a duration to decimal hours?

Divide the minutes portion by 60 and add it to the whole hours. For example, 2 hours 45 minutes = 2 + (45 / 60) = 2.75 decimal hours. This is useful for time-sheeting and payroll calculations where hours are recorded as a decimal number.

Clock Duration Calculator

Calculate the elapsed time between two clock times. Enter a start time and end time using hours, minutes, and AM/PM. The calculator shows the duration in hours and minutes, total minutes, and decimal hours. Durations that span midnight are handled automatically.

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Standard method Duration = end time minus start time (in total minutes). Overnight spans handled by adding 24 hours if end is before start.

1. Start Time

Time format

Start hour

2. End Time

End hour

Overnight span (end is next day)

Please enter valid times (hour 1-12 for AM/PM or 0-23 for 24-hour, minutes 0-59).

Elapsed Duration

Duration
8h 30m
Hours and minutes

Total Minutes

510

Elapsed minutes

Decimal Hours

8.50

For timesheets

Overnight?

Spans midnight

Calculation Breakdown

Start time-

End time-

Start (minutes since midnight)-

End (minutes since midnight)-

Overnight adjustment-

Elapsed minutes-

Duration in Different Units

Hours and minutes-

Decimal hours-

Total minutes-

Total seconds-

Fraction of a day-

Fraction of a week-

Result: Enter your start and end times above to calculate the duration.

How to Calculate Duration Between Two Times

The duration between two clock times is found by converting both times to the total number of minutes since midnight, then subtracting the start from the end. If the result is negative (meaning the end time is earlier in the day than the start time), add 1,440 minutes (the number of minutes in 24 hours) to get the correct overnight duration.

The Formula

Convert each time to minutes since midnight:

Minutes since midnight = (hour x 60) + minutes
For AM/PM, convert to 24-hour first: 12 AM = 0, 1 AM = 1, ..., 12 PM = 12, 1 PM = 13, ..., 11 PM = 23

Then: Elapsed minutes = End minutes - Start minutes

If Elapsed minutes is negative or you have selected "next day": Elapsed minutes = Elapsed minutes + 1,440

To convert elapsed minutes to hours and minutes: Hours = floor(Elapsed / 60), Minutes = Elapsed mod 60

To convert to decimal hours: Decimal hours = Elapsed minutes / 60

AM/PM to 24-Hour Conversion

12-hour	24-hour	Minutes since midnight
12:00 AM (midnight)	00:00	0
6:00 AM	06:00	360
9:00 AM	09:00	540
12:00 PM (noon)	12:00	720
5:30 PM	17:30	1,050
11:59 PM	23:59	1,439

Worked Example

Default inputs: start 9:00 AM, end 5:30 PM.

9:00 AM = 9 x 60 + 0 = 540 minutes since midnight
5:30 PM = 17 x 60 + 30 = 1,050 minutes since midnight
Elapsed = 1,050 - 540 = 510 minutes
Duration = 510 / 60 = 8 hours 30 minutes (8.50 decimal hours)

This matches the calculator output of 8h 30m (510 total minutes, 8.50 decimal hours).

Overnight Duration Example

Start 10:00 PM, end 6:30 AM (next morning):

10:00 PM = 22 x 60 = 1,320 minutes since midnight
6:30 AM = 6 x 60 + 30 = 390 minutes since midnight
Elapsed = 390 - 1,320 = -930 minutes (negative, so add 1,440)
Elapsed = -930 + 1,440 = 510 minutes = 8 hours 30 minutes

Common Uses

Timesheets and payroll: calculate hours worked between clock-on and clock-off times, expressed as decimal hours for easy multiplication by an hourly rate.
Shift planning: determine the length of a shift, including night shifts that span midnight.
Travel: work out how long a journey takes between departure and arrival times.
Scheduling: find out how much time is available between two appointments or events.
Cooking and baking: calculate how long something has been in the oven or how long until the timer goes off.

Related Calculators

Maths and Stats Calculators: full hub of maths tools.
Time Duration Calculator: duration across multiple time segments.
Time Calculator: add or subtract hours, minutes, and seconds.
Add Business Days Calculator: add working days to a date.
Time Duration Between Times Calculator: detailed interval calculator.

Method: Standard time arithmetic. Duration in minutes = (end hour x 60 + end minutes) - (start hour x 60 + start minutes). If the result is negative, 1,440 minutes (24 hours) is added to reflect a span across midnight. Decimal hours = total minutes / 60.

This calculator works with clock times only and does not account for daylight saving transitions. For scheduling purposes that cross a daylight saving boundary, adjust times manually by one hour as appropriate.

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