Time Calculator for adding and subtracting time

Three ways to calculate with time

The time calculator has three modes:

• Add: a list of times, each with a plus or a minus. Add rows for as many times as you need. Every entry can include seconds (1:30:15), and you can type 2h 15m, 90m or 1.5 (hours) as well as 1:30.
• Clock time: a time of day plus or minus a duration, for questions like “what time is it 7 hours 45 minutes after 9:15 AM?” or “what time did I start if I finished at 5:00 PM after 8 hours?”
• From–to: the duration between two clock times, with an optional break to subtract. Overnight spans are counted into the next day.

The result updates as you type. In Add mode you also see the working, line by line, so you can check it against your own sum.

Why you can’t add times like normal numbers

An hour has 60 minutes, not 100. Typed into a normal calculator, 2.45 + 1.30 gives 3.75, but 2 hours 45 minutes plus 1 hour 30 minutes is 4 hours 15 minutes. Either add hours and minutes separately and carry every 60 minutes, or convert everything to minutes first:

1. 2:45 = 165 minutes, 1:30 = 90 minutes.
2. 165 + 90 = 255 minutes.
3. 255 ÷ 60 = 4 remainder 15, so 4:15.

The same works for subtraction, and it is how the calculator works internally: it counts in whole seconds and only turns the total back into hours and minutes at the end, so there are no rounding errors.

Time duration calculator: time between two times

In From–to mode, enter two clock times to get the duration between them, for example 9:15 AM to 5:00 PM = 7 h 45 m. If the end time is earlier than the start, the span runs past midnight: 10:00 PM to 2:30 AM is 4 h 30 m. You can subtract a break from the span.

Adding time to a clock time

To find a time of day, add the duration to the clock time and wrap past midnight. 9:15 AM plus 7:45 is 17:00, which is 5:00 PM. 10:30 PM plus 3 hours is 1:30 AM the next day; the calculator says “the next day” so the change of date is clear. Subtracting works the same way backwards: 8 hours before 5:00 PM is 9:00 AM.

Clock times are calculated without daylight saving time. On the night the clocks change, a real elapsed time can be one hour longer or shorter.

Results over 24 hours and in decimals

Totals over 24 hours stay in hours (for example 26:30), with the same total in days, hours and minutes underneath. Every result also comes in decimal hours, rounded to two places (7:40 = 7.67), which is what timesheets and invoices usually need. For a minute-by-minute table, see the decimal hours converter. If you are adding up working hours, the hours calculator subtracts breaks for you, and the time card calculator adds up a whole week with overtime.