Time Duration Calculator
Work out the duration between two times of day, including spans crossing midnight, and add or subtract hours and minutes.
How it works
The duration is the difference between two times expressed in minutes, then formatted back into hours and minutes. Working in minutes throughout avoids the base-60 mistakes that come from treating 1.5 hours as 1 hour 50.
A span that crosses midnight is the case people get wrong. From 22:00 to 06:00 is eight hours, not minus sixteen — when the end time is earlier than the start, the tool assumes the next day rather than returning a negative.
The decimal hours figure is there for timesheets and invoicing, which almost always want 7.5 rather than 7:30. Those are the same duration written two ways, and mixing them up is a common payroll error.
The formula
Duration
minutes = (end − start), + 1440 if it crosses midnight
As hours and minutes
hours = minutes ÷ 60, remainder = minutes mod 60
As decimal hours
decimal = total minutes ÷ 60
Worked examples
| Scenario | Working | Result |
|---|---|---|
| 09:00 to 17:30 | 510 minutes | 8h 30m — 8.5 decimal hours |
| 22:00 to 06:00 | Crosses midnight | 8h, not −16h |
| A shift minus a 45-minute break | 510 − 45 | 7h 45m — 7.75 hours |
When you'd use it
- Working out hours on a timesheet
- Calculating an overnight or split shift
- Converting worked time into decimal hours for invoicing
- Adding a duration to a start time
Common questions
How do I handle a shift that crosses midnight?
Enter the times as they are — the tool assumes the end time is on the following day when it is earlier than the start. 22:00 to 06:00 gives eight hours rather than a negative.
What is the difference between 7:30 and 7.5 hours?
Nothing — they are the same duration in different notations. 7:30 is 7 hours 30 minutes; 7.5 is the decimal form used on timesheets. The trap is reading 7:30 as 7.3, which loses 12 minutes.
Can I subtract a break?
Yes. Enter the break in minutes and it is taken off the total, which is what a timesheet normally needs.