Time Duration Calculator
Find the duration in hours and minutes between two clock times, with automatic rollover when the end time is past midnight.
Duration
8h 30m
8.50 hours · 510 minutes
Formula
Duration = End time − Start time (add 24h if end is earlier than start)
Worked example
Start 09:00, end 17:30.
- End minutes since midnight: 17 × 60 + 30 = 1050
- Start minutes: 9 × 60 = 540
- Difference: 1050 − 540 = 510 min = 8h 30m
Answer: 8 hours 30 minutes
How it works
Both times are converted to minutes since midnight, then subtracted. Working in plain minutes avoids fiddly hours-and-minutes arithmetic and keeps the result exact.
When the end time is earlier than the start time, the calculator adds 24 hours so an overnight shift like 22:00 to 06:00 returns 8 hours instead of a negative number.
This tool measures elapsed clock time only — it doesn't subtract breaks. For timesheet math with a break, use the Hours Worked Calculator.
Common mistakes
- Mixing 12-hour AM/PM with 24-hour entries and forgetting which one the device is using.
- Expecting the duration to subtract a lunch break — this tool measures raw end-minus-start time.
- Typing invalid times like 25:00 or 12:75 — the time field rejects them.
FAQ
- How do I include a break?
- Use the Hours Worked Calculator instead — it subtracts a break from the duration.
- Does it handle 12-hour times?
- Yes. Browser time inputs accept 12- or 24-hour entry depending on your device settings.
- What if end is before start?
- The calculator assumes the end time is on the next day and adds 24 hours, which is what you want for night shifts.
- Does it count seconds?
- No — clock-time inputs are limited to hours and minutes for everyday use.
- Is the result rounded?
- The minutes value is exact. The decimal hours figure is rounded to two decimals for readability.