Time Duration Calculator

Handles overnight spans correctly

Enter a start and end time and it returns the hours and minutes between them — including shifts that cross midnight, like a 10pm-to-6am overnight span, which a naive subtraction would get wrong. That example specifically comes out to 8 hours flat, since the calculation rolls over into the next day instead of returning a negative number.

Built for timesheets, work shifts, flight durations, or any time you need the actual elapsed time between two clock readings without doing the math by hand.

A note on payroll rounding

Some employers round timesheet entries to the nearest quarter-hour or six-minute increment rather than paying exact clock times — this tool gives the true elapsed duration, so if a paycheck looks different from what you calculated here, check whether your employer's rounding policy is the difference before assuming an error. It also doesn't adjust for daylight saving time transitions, since it works from clock times rather than calendar dates.

Converting hours and minutes to decimal hours

Most timesheet and invoicing software wants elapsed time as a decimal, not an hours-and-minutes pair — 8 hours 30 minutes needs to be entered as 8.5, not "8:30," and it's an easy conversion to get wrong under pressure. The rule is to divide the minutes by 60 and add that to the hours: 45 minutes becomes 0.75, 15 minutes becomes 0.25, and 20 minutes becomes roughly 0.33. Reading the hours-and-minutes result this tool gives and converting it that way is generally faster and less error-prone than trying to do the whole subtraction in decimal form from the start.

Where this gets used beyond timesheets

Elapsed-time math shows up well outside payroll: checking how long a flight or layover actually is from the departure and arrival times printed on a ticket, working out how long a recorded video call or podcast ran from its start and end timestamps, or figuring out sleep duration from a bedtime and wake time — that last one being the most common overnight-span case, since most people's sleep window crosses midnight. Any time two clock readings need turning into a single elapsed duration, this same subtract-and-handle-the-rollover logic applies, regardless of what the two times actually represent.