Time Duration Calculator
Calculate the exact span of time between two clock times or across calendar dates with decimal conversion.
How to Calculate Time Duration Manually
Calculating the exact duration between two clock times follows simple modular subtraction with base 60 borrowing:
Convert 12-hour AM/PM times into 24-hour notation (e.g. 05:45 PM becomes 17:45).
If end minutes are lower than start minutes, borrow 1 hour (60 minutes) from the end hour.
Subtract start hours from end hours and start minutes from end minutes.
Related Tools
Time Calculator
Add or subtract clock times, calculate arrival or departure points, and normalize time units.
Work Hours Calculator
Calculate daily shift hours, automatically deduct lunch breaks, and estimate gross paycheck earnings.
Time Card Calculator
Log 7-day Monday–Sunday work logs with daily break deductions, overtime threshold (>40h), and pay summary.
Frequently Asked Questions
Everything you need to know about calculating time, durations, and work shifts.
How do you calculate duration between two times?
Convert both times into seconds from midnight (Hours × 3600 + Minutes × 60 + Seconds). Subtract the start time seconds from the end time seconds. If the end time is past midnight, add 24 hours (86,400 seconds) to the end time before subtracting.
Does this handle durations across multiple days?
Yes. You can either enable the Cross-midnight toggle for single overnight shifts (such as 11:00 PM to 07:00 AM) or specify distinct start and end calendar dates for multi-day spans.
How do I convert duration into billable decimal hours?
Divide the total minutes by 60 and add that to the whole hours. For example, 3 hours and 45 minutes = 3 + (45 / 60) = 3.75 decimal hours.