Time Calculator
Find the duration between two times, or add and subtract hours and minutes from a time of day.
Duration
8 h 0 m
- Total minutes
- 480
Updates live as you type
Frequently asked questions
Use duration mode: enter the start and end times in 24-hour format. The result shows hours and minutes, and the total in minutes.
Turn on “crosses midnight”. A shift from 22:00 to 06:00 then correctly returns 8 hours instead of a negative value.
Switch to add/subtract mode, set the direction, amount and unit. The calculator returns the new time and flags if it rolls into another day.
Enter times in 24-hour HH:mm format, such as 09:30 or 17:45, for unambiguous results.
06:00 minus 22:00 looks negative — it isn't
A shift from 22:00 to 06:00, with crosses midnight switched on, correctly returns 8 hours 0 minutes — 480 total minutes. Without that toggle, subtracting 22:00 from 06:00 directly produces a negative duration, since 06:00 is numerically "earlier" in the day than 22:00 even though the shift clearly ran forward through the night. The toggle is what tells the calculation to wrap across the day boundary instead of reading the two times as if they sat on the same calendar day.
Why clock arithmetic breaks so easily by hand
Time is fiddly specifically at boundaries — midnight rollovers, the switch between AM and PM, adding minutes that push a time past 23:59 — because the numbers don't increase monotonically the way a simple subtraction expects. This calculator handles two distinct versions of that problem: duration mode finds the gap between a start and end time in hours and minutes, while add/subtract mode shifts a single time of day forward or backward by a chosen number of minutes or hours.
What "rolls into another day" actually catches
In add/subtract mode, adding 90 minutes to 23:15 correctly rolls forward to 00:45 the next day rather than producing an invalid "24:45" — and the calculator flags explicitly whenever a shift crosses into the previous or next day, so that rollover is visible rather than silently baked into a time that looks plausible but is actually a day off.
This tool is ideal for timesheets, shift planning, study and workout session lengths, cooking schedules and travel timings where clock arithmetic across a boundary is easy to get wrong by hand. For paid extra hours, the overtime pay calculator turns a duration figure into actual earnings; for whole-day arithmetic across the calendar rather than within a single day, the date calculator is the right tool instead.