Durations and clock arithmetic
Two time questions come up constantly: how long is it between two clock times, and what time is it a few hours from now? This calculator answers both. In duration mode it subtracts two times of day — a shift, a flight, a study session — and reports the gap in hours and minutes, total minutes, total seconds and decimal hours. In add/subtract mode it moves a clock time forward or backward by any number of hours and minutes, wrapping cleanly over midnight. Durations that cross midnight are handled the way people mean them: an end time earlier than the start means the next day, so 22:00 to 06:30 is 8 hours 30 minutes, not an error.
How it works
Clock arithmetic fails when you subtract the columns separately (17:45 minus 09:30 is not 8 hours 15 by borrowing luck every time — try 17:10 minus 09:50). Converting everything to minutes first makes it one clean subtraction; a negative duration in "between" mode gets 1,440 minutes (a full day) added, which is exactly the overnight assumption. Decimal hours (8.25 rather than 8:15) are shown because timesheets and billing usually need them.
Everyday uses
Timing a work shift for a timesheet, checking whether a layover is long enough, adding cooking or curing times, working out sleep duration, or totalling a journey in legs. For durations measured in days rather than hours, the Date Difference Calculator counts the calendar side, and for moments in other time zones, use the Time Zone Converter.
Worked example
From 09:30 to 17:45 is 8 hours 15 minutes — 495 minutes, 29,700 seconds, or 8.25 hours in decimal form.
How to use this calculator
- Choose the mode: duration between two times, or add/subtract time.
- For a duration, enter the start and end times (an earlier end time counts as the next day).
- For add/subtract, enter the starting time and the hours and minutes to move.
- Read the result in the green panel and the totals in every unit in the table.
Decimal hours for timesheets
Payroll systems rarely accept "8:15"; they want 8.25. The rule: decimal hours = hours + minutes ÷ 60, so every 6 minutes is 0.1 of an hour. Common landmarks: 15 min = 0.25, 20 min ≈ 0.33, 30 min = 0.50, 45 min = 0.75. The breakdown table above always shows the decimal form of your duration alongside the clock form. Adding up several shifts, legs or recipe times at once? The Time Calculator adds and subtracts hours, minutes and seconds directly.