About the Time Duration Calculator
The Time Duration Calculator answers two of the most common time-related questions: "how long is it between time A and time B?" and "what is time X plus or minus duration Y?". Both modes work with hours, minutes and seconds, and support overnight shifts and negative results.
Mode 1 — Between two times
Enter the start and end clock times. If the end time is on the next day (a night shift, an overnight flight, a long task that crosses midnight), tick the "next day" box and the calculator will add 24 hours to the end time before subtracting. The result is shown in HH:MM:SS, and also broken out as total hours, total minutes, total seconds and decimal hours (useful for invoicing and timesheets).
Mode 2 — Add or subtract
Enter a base duration (or time interval) and a second duration to add or subtract. The result is normalised so 90 minutes becomes 1 hour 30 minutes automatically. Negative results are returned with a clear minus sign — useful for "how much over budget am I?" planning.
Common uses
- Timesheets and payroll — total hours worked across a shift, with breaks subtracted
- Cooking and baking — when does the roast come out if it goes in at 14:30 and needs 3h 45m?
- Fitness intervals — total session length from individual splits
- Exam time-management — what's the cutoff if I start at 09:00 and have 2h 30m?
- Travel — flight time across time zones (use 'next day' for overnight legs)
- Music/podcast/video editing — running total of clip lengths
Frequently Asked Questions
How is duration between two times calculated? Both times are converted to total seconds; the calculator subtracts and re-expresses the answer in HH:MM:SS plus the equivalent in hours, minutes, seconds and decimal hours.
How do I add a shift that runs past midnight? Tick "End time is on the next day". The calculator then treats the end time as belonging to the following calendar day, so 22:30 → 06:00 returns 7 hours 30 minutes rather than a negative result.
Why is decimal hours useful? Many payroll and timesheet systems expect decimal hours (e.g. 7.5 instead of 7:30). The calculator displays both formats so you can copy whichever your system needs.
Can the calculator subtract a longer time from a shorter one? Yes — the result will simply be negative, with a leading minus sign. This is useful for planning ("how much over budget am I?") and for tracking pace differences.
How many hours are between two times? Enter the start and end time and the calculator returns the gap in hours and minutes — for example, 9:00 to 17:30 is 8 hours 30 minutes, or 8.5 decimal hours. If the end time is earlier than the start, tick the next-day option.
How do I add or subtract hours and minutes from a time? Switch to add/subtract mode, enter a starting clock time, then the hours, minutes and seconds to add or remove. The calculator rolls the clock correctly across midnight and shows the resulting time of day.
Is the data shared anywhere? No. All calculations run entirely in your browser and nothing is uploaded.
Related Calculators
- Date Difference Calculator — Days, weeks, months and years between two dates. Add or subtract days from a date and get the day of the week.
- Age Calculator — Exact age in years, months and days, total days lived and days until your next birthday.
- Time Zone Converter — Convert any date and time to multiple time zones simultaneously. DST-aware, all IANA zones supported.