Time Duration Calculator
Work out the hours and minutes between two clock times, including overnight shifts that cross midnight.
How it works
duration = end − start · if negative, add 24 h (the span crosses midnight)
Both times are converted to minutes since midnight and subtracted. When the end time is earlier on the clock than the start time, the span is assumed to cross midnight, so 24 hours are added — a 22:15 start and 6:45 end reads as an overnight shift, not a negative number. Identical start and end times read as zero, not 24 hours.
Worked example
A shift from 22:15 (10:15 PM) to 6:45 AM: 6:45 is earlier on the clock, so add 24 hours — 30:45 minus 22:15 gives 8 hours 30 minutes, or 8.50 decimal hours.
Frequently asked questions
How do I enter 12-hour times?
Convert to the 24-hour clock: AM hours stay as they are (12 AM becomes 0), and PM hours add 12 — so 5:30 PM is hour 17, minute 30.
Why show decimal hours?
Payroll systems multiply an hourly rate by decimal hours, and 7 hours 30 minutes is 7.5 — not 7.3. The decimal row saves that conversion.
What about a full 24-hour span?
Equal start and end times read as 0 because the calculator cannot tell “no time” from “a full day”. For a 24-hour duration, split it or add 24 hours to a partial result.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.