How Time Duration Calculator Works
Both times are converted to minutes since midnight, and the start is subtracted from the end. If that comes out negative — meaning the end time is earlier in the clock than the start time — the tool assumes the shift crossed midnight and adds a full 24 hours (1,440 minutes) before showing the result, rather than reporting a negative duration.
How to Use This Tool
- Enter the time the shift, task or event started.
- Enter the time it ended.
- Select Calculate Duration to see the total length in hours and minutes, plus the total in minutes.
Example
A shift starting at 10:00 PM and ending at 6:00 AM the next day lasts 8h 0m — the tool detects the end time is earlier than the start and automatically counts it as crossing midnight, for a total of 480 minutes.
Helpful Tips
- For a same-day span, just enter both times normally — no extra steps needed.
- For an overnight shift, enter the end time as it appears the next morning; the tool will handle the day rollover for you.
- If a duration doesn't look right, double check whether you meant AM or PM — the time input uses your browser's local time format.
Frequently Asked Questions
How does the tool know a shift crossed midnight?
If the end time is earlier in the day than the start time, it assumes the end time falls on the next calendar day and adds 24 hours automatically.
Can I calculate a shift longer than 24 hours?
Not directly — this tool is built for single start and end clock times within a day-and-a-bit span. For multi-day durations, use a date-based calculator instead.
Does the result account for breaks?
No, it calculates the raw duration between the two times you enter. Subtract any break time from the total yourself if needed.
What if I enter the same time for start and end?
The tool reports a duration of 0h 0m, since no time has elapsed between identical start and end times.
This tool runs entirely in your browser. Your input is not uploaded to any server.