Time Duration Calculator
Work out the hours, minutes and seconds between two clock times — 24-hour or AM/PM, across midnight or several days, minus a break — or add or subtract a duration to find an end or start time.
How it works
duration = end − start · if the end is earlier on the clock, add 24 h (crosses midnight) · + 24 h for each extra day · − break · end time = start + duration · start time = end − duration
Both times are turned into minutes (or seconds) after midnight and subtracted. When the end time is earlier on the clock than the start, the span is taken to cross midnight, so 24 hours are added — a 22:15 start and 06:45 end is an overnight shift, not a negative number. For spans longer than a day, set how many days later the end is; 1 day later with the same clock time gives exactly 24 hours. An optional break is taken off the total. The result is shown in hours and minutes, hh:mm, decimal hours for payroll, total minutes and seconds. The other two modes work the other way: add a duration to a start time to find when something ends, or subtract it from an end time to find when to start, with the day shift shown when you cross midnight. You can type times on the 24-hour clock or with AM/PM, and add seconds under More options.
Worked example
A shift from 22:15 (10:15 PM) to 06:45 (6:45 AM): converted to minutes, the start is 22 × 60 + 15 = 1,335 and the end is 6 × 60 + 45 = 405. The end is earlier on the clock, so add 1,440 minutes: 1,845 − 1,335 = 510 minutes — 8 hours 30 minutes, or 8.50 decimal hours. With a 30-minute break it is 8 hours, and 8 hours 30 minutes after 22:15 is 06:45 the next day.
Frequently asked questions
Can I enter 12-hour times?
Yes — switch the clock to 12-hour and pick AM or PM for each time. Hours from 13 to 23 are always read as 24-hour time, so 17 means 5 PM whichever clock you choose.
Why show decimal hours?
Payroll systems multiply an hourly rate by decimal hours, and 7 hours 30 minutes is 7.5 — not 7.3. The decimal row saves that conversion.
How do I get a full 24-hour or multi-day span?
Identical start and end times read as 0. Under More options set “End is this many days later” to 1 for exactly 24 hours, or to 2 or more for longer spans; the result is then shown in days, hours and minutes as well.
How do I find what time it will be after a duration?
Choose “Start + duration”, enter the start time and the hours and minutes to add. “End − duration” works backwards, for example to find when to start cooking so a 3 h 45 min recipe is ready by 18:00.
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This calculator is for educational purposes. Double-check important results before acting on them.