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Finding the time between two clock times looks simple, but two things trip people up: minutes run in base 60 (1.5 hours is "1 hour 30 minutes," not "1.30"), and intervals that cross midnight. How long a shift ran, a flight's duration, the length of a break — all can hit these two traps.
Enter a start and end time (HH:MM), and the duration is calculated in hours and minutes, correctly even across midnight.
Time Duration Calculator: step-by-step worked example
- Start time (HH:MM)
- 09:15
- End time (HH:MM)
- 17:40
- 1
Convert times to minutes
Minutes = Hours × 60 + Minutes
09:15 → 555 · 17:40 → 1,060 = 505 min
- 2
Add 24 h if it crosses midnight
If difference < 0: difference + 1,440 min
505 ≥ 0 → nothing added = 505 min
- 3
Hours
Hours = ⌊Total min ÷ 60⌋
⌊505 ÷ 60⌋ = 8 h
- 4
Remaining minutes
Minutes = Total min − Hours × 60
505 − 8 × 60 = 25 min
- Same day505 min100%
Good to know: If the end time is earlier than the start, the range is assumed to run past midnight (22:30 → 06:15 = 7 h 45 min). Use a date-based calculator for spans over 24 hours.
Time Duration Calculator — how it works
How it's calculated
Both times are converted to minutes (hours × 60 + minutes), the difference is taken, and it's converted back to hours and minutes. 09:30 = 570 minutes, 17:45 = 1,065 minutes; the difference is 495 minutes = 8 hours 15 minutes.
Intervals that cross midnight
If the end time is earlier than the start (e.g. 22:00 to 06:00), the interval has crossed midnight; 24 hours are added to the end. So 22:00 → 06:00 is not −16 hours but 8 hours. This is the most common mistake in night shifts and flights.
Time is not decimal
The most frequent confusion: 1 hour 30 minutes is "1.5 hours," but writing 1 hour 30 minutes as "1.30" and adding is wrong. 90 minutes = 1.5 hours; you convert to decimals by dividing minutes by 60. That matters wherever decimals are needed, such as pay calculations.
Common uses
- Work/shifts: hours worked (including night shifts).
- Flights/travel: elapsed time between two clock times (same time zone).
- Breaks/events: how long an activity lasted.
For durations spanning different DAYS, a days-between or days-until calculator is the right tool; this one is for same-day (or single overnight) time intervals.
Worked example
A shift from 09:30 in the morning to 17:45 in the evening: 09:30 = 570 minutes, 17:45 = 1,065 minutes; the difference is 495 minutes = 8 hours 15 minutes (subtract any break separately). For a night shift starting at 22:00 and ending at 06:00: since the end is earlier than the start, midnight has been crossed, 24 hours are added to the end, and the duration comes out as 8 hours — subtracting "06:00 minus 22:00" directly would give the wrong answer.
Frequently asked questions
How do I calculate the duration between two times?+
Both times are converted to minutes, the difference is taken, and it's converted back to hours and minutes. 09:30 to 17:45 is 495 minutes, or 8 hours 15 minutes.
How is a duration across midnight calculated?+
If the end time is earlier than the start, midnight has been crossed and 24 hours are added to the end. So 22:00 → 06:00 is calculated as 8 hours. The tool does this automatically.
Why is 1 hour 30 minutes 1.5 hours and not 1.30?+
Time is base 60, not decimal. 30 minutes is half an hour, so it equals 0.5: 1 hour 30 minutes = 1.5 hours. You convert minutes to decimals by dividing by 60.
Can I calculate a shift length with this?+
Yes — enter the start and end time and it gives the duration, including night shifts. Subtract break time from the result separately.
Does it handle two times on different days?+
This tool is for same-day or single-overnight intervals. For durations spanning multiple days, use a days-between-dates calculator.
Does it show the time-zone difference between cities?+
No — this tool finds the duration between two clock times, not the UTC offset between time zones. City-to-city time-zone differences are a separate matter.
Related guides
About this page
- Publisher:
- Kalkoro — Teknolojig Bilişim Teknolojileri A.Ş., İstanbul
- Written by:
- Ahmet Tur — Editor (Math, date & time, unit conversion, physics & chemistry, everyday tools)
- Reviewed by:
- Kübra Yıldız — Editor
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