Time Duration Calculator

Convert both times to minutes since midnight, then subtract the start from the end. For example, 09:00 is 540 minutes and 17:30 is 1050 minutes, so 1050 minus 540 is 510 minutes, which is 8 hours and 30 minutes. If you took a break, subtract those break minutes from the total before converting back to hours and minutes.

Work out the gross duration between the start and end times first, then take the break off in minutes. A shift from 09:00 to 17:30 is 8 hours 30 minutes gross, so a 30 minute lunch leaves 8 hours of paid or billable time. The calculator above handles this for you when you enter a break value, so the result is always the net duration.

Divide the minutes by 60. So 15 minutes is 0.25 hours, 30 minutes is 0.50 hours, and 45 minutes is 0.75 hours. For a mixed duration like 8 hours 30 minutes, keep the whole hours and add the decimal share of the leftover minutes, giving 8.50 hours. Decimal hours are what most billing and payroll systems expect.

When the end time is earlier than the start time, the shift has rolled past midnight, so add 24 hours to the end time before subtracting. A shift from 22:00 to 06:00 looks like a negative number until you treat 06:00 as the next day, which gives 8 hours. The calculator detects this automatically and shows a note when it has assumed the end time is on the following day.

The hh:mm format splits time into hours and whole minutes, which is how a clock reads. Decimal hours express the same span as a single number where the fraction is a share of an hour, so 7 hours 45 minutes becomes 7.75. They describe the same duration. People read hh:mm more easily, but billing, timesheets and payroll almost always work in decimal hours.

Add the minutes of every duration together first, then convert the total back into hours and minutes at the end. Adding the hh:mm values directly is where mistakes creep in, because 45 minutes plus 30 minutes is 75 minutes, which rolls over into an extra hour. Summing in minutes, or in decimal hours, avoids the rollover problem entirely.

Billing multiplies time by a rate, and multiplying a decimal is far simpler than multiplying hours and minutes separately. At a rate of 120 per hour, 1.5 hours is plainly 180, while 1 hour 30 minutes invites errors. Decimal hours also add up cleanly across many entries, which is why invoices, timesheets and accounting tools store time this way.

Pick one rounding rule and apply it consistently. Common choices are rounding to the nearest 6 minutes (a tenth of an hour), the nearest quarter hour, or not rounding at all. Rounding every entry the same way keeps totals fair and predictable. Whatever you choose, agree it with clients up front so the rounded duration on the invoice is never a surprise.

Enter your clock-in time as the start and your clock-out time as the end, then enter your unpaid break in minutes. The result is your net hours worked for the day, shown in both hh:mm and decimal hours. To total a week, calculate each day, add the minutes together, and convert once at the end. The time card calculator does this across a full week.

This tool is built for a single span between two clock times, so it assumes any end time earlier than the start falls on the next day. That covers normal day and overnight shifts up to 24 hours. For anything spanning multiple days, split it into per-day durations and add the minutes together, which keeps each figure accurate.

A zero result usually means the break you entered is equal to or larger than the gap between the start and end times, or that one of the time fields is empty. Check that both times are filled in and that the break in minutes is smaller than the total span. The calculator never returns a negative duration, so it clamps at zero instead.

Yes. Use the copy link button under the inputs and the calculator saves your start time, end time and break into the web address. Anyone who opens that link sees the same numbers you do, which is handy for confirming a shift or a billable block with a colleague or client without re-typing anything.