Understanding your result
The result subtracts the starting clock time from the ending clock time. When next day is selected, one 24-hour day is added if the interval crosses midnight or the times match.
For a person’s age in complete calendar years, months, and days, use the Age Calculator with their birth date and the comparison date.
The formula
Each time is converted to minutes after midnight. The total converts back to hours and minutes and is also divided by 60 for decimal hours.
An overnight interval
From 10:30 PM to 1:15 AM the next day is 2 hours 45 minutes, or 165 minutes and 2.75 decimal hours.
How to use this calculator
- Enter the start and end times.
- Select next day if the interval passes midnight.
- Calculate to see hours and minutes, total minutes, and decimal hours.
Use decimal hours for time records
Minutes are parts of 60, so 30 minutes is 0.5 hour and 45 minutes is 0.75 hour.
Decimal hours can help with timesheets, but payroll systems may apply their own rounding increments.
Make midnight explicit
An ending clock time earlier than the start is ambiguous without a date. The next-day option identifies an overnight interval.
Matching times mean zero duration on the same day or 24 hours when next day is selected.
Assumptions & limitations
What this calculation assumes
- Times use a single 24-hour cycle.
- An overnight interval spans at most one day.
- No break time is deducted.
What to keep in mind
- Dates, time zones, and daylight-saving changes are not modeled.
- Payroll rounding rules are not applied.
- Intervals longer than 24 hours require a date-based calculation.
Common questions
Why is an earlier end time rejected?
Select the next-day option to show that the interval crosses midnight.
Is 8 hours 30 minutes equal to 8.3 hours?
No. Thirty minutes is half an hour, so the decimal value is 8.5.
Does the calculator subtract lunch?
No. Calculate each working interval separately if you need to exclude breaks.