Time Calculator
Three time jobs in one place: arithmetic on durations, the gap between two clock times, and totalling a timesheet into decimal hours.
| Decimal hours | — |
| Total minutes | — |
| Total seconds | — |
How to use the Time Calculator
- Pick a mode: duration arithmetic, the gap between two clock times, or totalling a list.
- Fill in the fields. In list mode, put one duration per line as
7:45,7:45:30or7.75. - Press Calculate. Every result is also shown as decimal hours for payroll and invoicing.
Why time arithmetic goes wrong in spreadsheets
Time is base 60, not base 10, and this is the source of most timesheet errors. Three hours and 45 minutes is 3.75 decimal hours, not 3.45. Anyone typing 3.45 into an invoice at an hourly rate underbills themselves by 18 minutes.
The conversion is minutes ÷ 60. Fifteen minutes is 0.25, twenty minutes is 0.333…, and 50 minutes is 0.8333…. Every result here shows both forms so you can copy whichever your system expects.
Overnight shifts and negative results
A shift from 22:00 to 06:00 produces a negative number if you subtract naïvely, because the end time is a smaller clock value. The fix is adding 24 hours when the end precedes the start — which this tool does automatically, and which the "next day" checkbox forces when a shift is longer than 24 hours.
One caveat: on days when daylight saving starts or ends, a wall-clock day is 23 or 25 hours long. Clock-time arithmetic assumes 24. For payroll spanning a changeover date, check the affected shift by hand.
Frequently asked questions
How do I convert minutes to decimal hours?
Divide by 60. Ninety minutes is 1.5 hours; 20 minutes is 0.333 hours. Every result here includes the decimal figure to four places.
Can I total a week of shifts at once?
Yes — use "Total a list" and paste one shift per line. Mixed formats work, so 7:45 and 7.75 can appear in the same list.
What if a result is negative?
In duration mode it means the second value is larger, and the result is shown with a minus sign. In clock mode a negative gap is treated as crossing midnight.
Does it handle durations longer than 24 hours?
Yes. Durations are not clock times, so 30h 15m is displayed as-is rather than wrapping around.
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