Time Calculator
Add and subtract hours, minutes and seconds, or work out what time it will be after a set duration.
How it works
In duration mode, enter as many rows of days, hours, minutes and seconds as you need, each with a + or − sign.
Values roll over automatically, 90 minutes becomes 1 hour 30 minutes. Totals are also shown in decimal hours, minutes and seconds.
In clock mode, enter a start time and a duration to add or subtract. We show the end time and whether it lands on a different day.
Formula
total seconds
Where:
- d, h, m, s
- = Days, hours, minutes, seconds in each row
- mod 24 h
- = Wraps around midnight
Worked example
Two tasks take 2 h 45 min and 3 h 30 min.
45 + 30 = 75 minutes = 1 h 15 min, so the total is 6 h 15 min (6.25 hours). And 10:30 PM plus 5 h 45 min is 4:15 AM the next day.
Summing Durations for Productivity
The Time Calculator is designed for adding up multiple segments of time, such as podcast episodes, flight legs, or individual tasks in a project workflow. By adding multiple rows, it eliminates the need for complex mental math or manually converting everything to minutes before adding them up for a total.
It is also highly effective for basic clock math and scheduling. If you know a meeting starts at 2:15 PM and will last 1 hour and 50 minutes, the tool quickly provides the exact end time. This prevents common errors like forgetting to flip from AM to PM or miscalculating the hour rollover.
Time vs. Time Duration Calculator
The Time Calculator is for abstract quantities of time, adding 2 hours here and 30 minutes there. It does not care about the specific calendar date. The Time Duration Calculator is date-specific and considers geographical locations. Use this for building schedules and the other for measuring exact cross-calendar spans.
If your calculation involves crossing into a new day or traveling between time zones, the Duration tool is essential. If you are simply adding up tasks on a daily to-do list, the standard Time Calculator is faster. Using the wrong tool can lead to missing the impact of daylight saving time changes.
Avoiding Decimal Conversion Errors
A classic mistake in time math is treating minutes like decimals. For example, 7 hours and 30 minutes is 7.5 hours, not 7.3. This tool shows both the traditional H:M:S format and the decimal equivalent, ensuring you have the correct data for payroll, billing, or time-tracking systems.
When subtracting time, ensure you are using the correct sign for each row. Subtracting a longer duration from a shorter one results in a negative total. The tool handles these negative durations gracefully, which is useful when finding 'time remaining' in a fixed time budget or a countdown scenario.
Frequently asked questions
Divide by 60. For example, 45 minutes is 0.75 hours, so 6 h 45 min is 6.75 hours.