Working out a duration from clock times is easy to get wrong when it crosses noon or midnight, or when you mix minutes with decimal hours (7 h 30 min = 7.5 h, not 7.3 h). This calculator handles both 12- and 24-hour clocks – just pick the times.
How to use the Time Duration Calculator
- Start time
- End time
- Breaks
Results update as you type, and every field accepts the units shown in its menu.
How it works
Pick the start and end times and enter any break.
Tips
- Check whether the end date should be included – event durations usually include it, elapsed time does not.
- Months have 28–31 days, so “one month” is counted by calendar date, not as 30 days.
- Use 24-hour time or set AM/PM carefully when entering clock times.
- Time zones and daylight-saving changes are not applied unless the calculator says so.
Common mistakes to avoid
- Counting a 30-day month when a calendar month is meant (or the reverse).
- Forgetting leap years when counting days across February.
- Mixing decimal hours (7.5 h) with clock time (7:30).
Inputs explained
| Field | What to enter |
|---|---|
| Start time | A clock time (hours and minutes) |
| End time | A clock time (hours and minutes) |
| Breaks | In min |
What each result means
- Elapsed time = mod([End time] – [Start time], 24)
- Duration = [Elapsed time] – [Breaks]÷60
- Decimal hours = [Duration]
- Total minutes = [Duration]×60
- Share of a day = [Duration]÷24×100
Formula
Duration = end time − start time (+ 24 h if the end is past midnight) − breaksDecimal hours = hours + minutes ÷ 60Worked example
Inputs — Start time: 09:15; End time: 17:45; Breaks: 30 min.
Results — Elapsed time = 8 h 30 min; Duration = 8 h 0 min; Decimal hours = 8; Total minutes = 480; Start (12-hour clock) = 9:15 AM; End (12-hour clock) = 5:45 PM; Share of a day = 33.3 %.
Frequently asked questions
How do I calculate time between two times?
Subtract the start from the end; if the result is negative, add 24 hours.
How many hours from 9:15 am to 5:45 pm?
8 h 30 min, or 8.5 hours.
How do I convert minutes to decimal hours?
Divide by 60 – 45 minutes is 0.75 h.
What formula does the Time Duration Calculator use?
Duration = end time − start time (+ 24 h if the end is past midnight) − breaks.