Writing and time tools
Time Calculator
Calculate time between clock times, subtract breaks, add or subtract durations, or convert decimal hours. Get hours, minutes, seconds and a copyable result.
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How to use this tool
1. Choose clock times, a list of durations, or decimal hours. Only the relevant inputs are shown.
2. For an overnight interval, explicitly select Next day. Enter any break in whole minutes. For lists, use one H:MM or H:MM:SS duration per line.
3. Calculate to see a duration, decimal hours and total seconds. Copy or print a report; editing inputs clears the previous result.
How time is calculated
Clock times are converted to seconds after midnight. Next day adds 86,400 seconds to the end time; the start time and break are subtracted. Duration lists sum signed seconds. Decimal hours are multiplied by 3,600 and rounded to the nearest second.
Worked examples
09:00 to 17:30 with a 30-minute break is 08:00:00, or 8 decimal hours. Adding 1:30 and 2:45, then subtracting 0:15, gives 04:00:00. Decimal 1.5 hours is 01:30:00.
Questions and assumptions
Dates, daylight saving and payroll
This is clock and duration arithmetic. It does not account for dates, daylight-saving transitions, time zones, payroll rules or paid-break policies. Use the date calculator for calendar-day differences.
Limits and precision
Equal clock times mean zero on the same day or 24 hours on the next day. Lists accept up to 100 entries with at most five hour digits each. Decimal input accepts 0–100,000 hours and six decimal places; decimal-hour output shows up to six places.
Sources and further reading
Built and maintained by Custom Logic. Page updated .