Use this calculator to find how much time passes between a start time and end time, including overnight spans and optional break deduction.
Advanced options
Break and detail
Number formatting
How to use our Time Duration Calculator
- Choose Time format, then enter Start time and End time. In 12-hour mode, also choose Start period and End period.
- Set End time is on the next day to Yes only when the ending time happens after midnight, such as 10:00 PM to 6:00 AM.
- If needed, open Advanced options and enter Break time (minutes). Turn on Include seconds in results if you want total seconds shown.
- Click Calculate to see Net duration, Decimal hours, Total minutes, and other results.
- Sanity-check the answer: make sure Overnight handling matches your situation and confirm that Duration before break minus Break deducted equals the Net duration.
Definitions
Duration: How much time passes from Start time to End time.
Net duration: The final elapsed time after any Break time (minutes) is removed.
Duration before break: The raw time difference before break deduction.
Decimal hours: The same duration written as a decimal number of hours, such as 8.25 hours.
Total minutes: The full net duration converted into minutes.
Total seconds: The full net duration converted into seconds when that result is turned on.
Overnight handling: Whether the calculator treated the End time as happening on the next day.
12-hour time: Clock time with AM or PM, such as 9:00 AM or 5:00 PM.
24-hour time: Clock time without AM or PM, such as 09:00 or 17:00.
Common mistakes and quick fixes
Mistake: Entering 24-hour times while Time format is set to 12-hour, or mixing up AM and PM in Start period or End period .
Fix: If you want to type times like 13:20 or 16:05, switch Time format to 24-hour. If you stay in 12-hour mode, double-check both period selectors.
Mistake: Leaving End time is on the next day set to No when the ending time is after midnight.
Fix: Turn End time is on the next day to Yes for overnight spans such as 10:00 PM to 6:00 AM.
Mistake: Typing a negative value in Break time (minutes) .
Fix: Enter 0 or a positive number only. Break time is deducted from the duration, so it cannot be negative.
Mistake: Making Break time (minutes) larger than Duration before break .
Fix: Reduce the break so it is less than or equal to the full time span before deduction.
Mistake: Reading Decimal hours as hours and minutes.
Fix: Treat Decimal hours as a base-10 number for payroll or spreadsheets. For example, 7.5 means 7 hours 30 minutes, not 7 hours 50 minutes.
Mistake: Expecting Total seconds to appear when Include seconds in results is set to No.
Fix: Change Include seconds in results to Yes if you need the duration converted to seconds.
Limitations & Key Assumptions / Boundary Conditions
- This tool measures duration between clock times only. It does not use calendar dates, time zones, daylight saving changes, or travel-time adjustments.
- If Time format is set to 24-hour, the calculator ignores Start period and End period.
- The calculator does not guess overnight spans automatically. If the end time is earlier than the start time, you must set End time is on the next day to Yes.
- Break time (minutes) must be 0 or more and cannot be greater than the duration before break.
- If Start time equals End time and overnight is No, the result is 0 minutes. If overnight is Yes, the result is 24 hours before any break is deducted.
- When seconds are not part of the input, calculations treat seconds as 0, so results should not be read as more precise than the times entered.
Methodology
How the calculator works
The calculator finds the elapsed time between two clock times, then subtracts any optional break. It also converts the final answer into decimal hours, total minutes, and sometimes total seconds.
Step 1: Convert each time to minutes after midnight
minutes = hour24 * 60 + minute + second / 60
If you are using 12-hour time, the calculator first changes the entered hour and AM or PM into 24-hour time. In this tool, seconds are treated as 0 because the inputs are clock times without seconds.
hour24 = hour12 mod 12; if period = PM then hour24 = hour24 + 12
This correctly turns 12:00 AM into 0:00 and 12:00 PM into 12:00.
Step 2: Find the duration before break
gross_minutes = end_minutes - start_minutes; if cross_midnight = yes then gross_minutes = gross_minutes + 1440
There are 1,440 minutes in a day, so overnight handling adds one full day when the ending time is on the next day. If overnight is set to No and the end time is earlier than the start time, the calculator shows an error instead of guessing your intent.
Step 3: Subtract the break
net_minutes = gross_minutes - break_minutes
If the break is larger than the duration before break, the calculator shows an error because the final duration cannot be negative for this use case.
Step 4: Convert the final result
decimal_hours = net_minutes / 60
total_seconds = net_minutes * 60
Net duration is shown in hours and minutes. Decimal hours is useful for payroll and spreadsheets, while Total minutes and Total seconds help with logs and exact conversions.
Mini example
Suppose Start time is 10:00 PM, End time is 6:30 AM, End time is on the next day is Yes, and Break time (minutes) is 30. Start time is 1320 minutes after midnight, end time is 390 minutes after midnight, and overnight handling adds 1440 minutes. That gives 510 gross minutes. After subtracting a 30-minute break, the net duration is 480 minutes, which equals 8 hours or 8.0 decimal hours.
Assumptions used
This calculator uses standard time-unit conversions: 60 minutes per hour, 60 seconds per minute, and 1,440 minutes per day. Real-world schedules can differ if calendar dates, daylight saving changes, or time-zone shifts matter, but those are outside this tool's scope.