Time Calculator
Add and subtract hours, minutes, seconds โ plus decimal hours.
About this calculator
Two jobs, both about base-60 arithmetic. Paste durations one per line โ h:mm:ss, h:mm, or bare minutes, with minus to subtract โ and get the sum plus its decimal-hours form. Or give two clock times and read the gap, with across-midnight handled for night shifts.
Decimal hours, and the billing error everyone makes
Timesheets and invoices bill in decimal hours, and the conversion is the classic trap: 7 hours 25 minutes is 7.42 hours, not 7.25 โ minutes divide by 60, and writing them after the decimal point directly is the mistake this tool exists to prevent. (The reverse trap too: 7.5 hours is 7:30, not 7:50.) Why time is base-60 at all: the Babylonians, whose 60 divides cleanly by 2, 3, 4, 5, 6, 10, 12 โ genuinely convenient for fractions, genuinely awkward for addition, which is why the carry from 60 minutes trips everyone. Related machinery: the hours calculator for shift spans with breaks, the time tracker for logging as you go, and business days when the units grow.
Frequently asked questions
How do I add hours and minutes correctly?
Add minutes and carry every 60 into the hours: 1:45 + 0:30 = 2:15, not 1:75. Paste durations one per line here and the carrying is handled.
How do I convert time to decimal hours for a timesheet?
Divide the minutes by 60: 7:25 โ 7 + 25/60 = 7.42 hours. Writing 7.25 undercounts by ten minutes โ the most common billing error there is.
Can it handle overnight shifts?
Yes โ a To time earlier than From is read as crossing midnight, so 22:00 to 06:30 gives 8 h 30 min.
Can I subtract a duration?
Prefix a line with minus: entering 8:00 and -0:45 sums to 7:15 โ useful for deducting breaks.