Date & Time Tools New Tool

Free Online Time Duration, Add and Subtract Time Calculator

Work out how long it is between two clock times, or add and subtract hours, minutes and seconds from a time. Shifts that run past midnight are handled rather than giving a negative answer, and every result is shown as hours and minutes, as decimal hours, and as a plain number of minutes and seconds.

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Free Online Time Duration, Add and Subtract Time Calculator

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⏳ Time Duration, Add and Subtract Between two times · add or subtract · past midnight handled

Every date is worked out in your browser. Nothing you type is sent anywhere.

⏳ What do you need?

Start time

End time

Whole days in between, if the shift is longer than one night Leave this at 0 for an ordinary shift. The page already adds one day by itself when the end time is earlier than the start.

Try one of these

Duration

—

Hours and minutes—

Decimal hours—

Total minutes—

Total seconds—

In words—

Both times turned into seconds, then one subtraction.

Step	Value	What it means

The same answer as	Value	Where this form is used

Recent answers, kept in this browser only.

Nothing here yet Press Log to history on the Duration tab to keep an answer here.

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How to Work Out a Time Duration

Three steps, and the second one is where most answers go wrong.

Pick what you need The gap between two times, or a time with an amount added, or a time with an amount taken off. The three share one piece of arithmetic, so they share one page.

Enter the times If the end time is earlier than the start, the page treats it as the next day rather than handing back a negative number. For anything longer than one night there is a box for the whole days in between.

Read it in the form you need Hours and minutes for a rota, decimal hours for payroll, plain minutes or seconds for a log. 7 hours 45 minutes is 7.75 decimal hours, not 7.45, and both are shown so the two never get mixed up.

What to Know About Adding Up Time

Midnight, decimal hours and the mistakes they cause.

A night shift is not a negative duration. From 22:00 to 06:00 is eight hours. Subtracting the clock numbers gives minus sixteen, which is how a surprising number of rota spreadsheets end up with negative hours. This page adds a day when the end time is earlier than the start, and says on screen that it has done so, rather than quietly guessing.

Decimal hours are not hours and minutes with a dot. 7 hours 45 minutes is 7.75 hours, because 45 minutes is three quarters of an hour. Typing 7.45 into a payroll sheet is a real error of 18 minutes a day. Every answer here is given in both forms side by side for exactly that reason.

Minutes over 59 are allowed on purpose. When adding time there is no reason to make you convert 150 minutes into two and a half hours first. The boxes accept any whole number, so 0 days 0 hours 150 minutes works, and the page shows what it read that as.

Seconds are kept, not rounded away. The whole calculation runs in seconds, so a duration of 1:23:45 stays exact. If the times you enter have no seconds the answer simply ends in zero, and the seconds row is still there when a log or a recording needs it.

Clock time is not the same as elapsed time when the clocks change. On the day daylight saving starts or ends, a shift from 22:00 to 06:00 is seven or nine hours of real time, not eight. This page works on plain clock arithmetic, which is what a rota and a timesheet use. For an answer that follows a particular time zone through its own clock change, the time zone converter is the page for that.

It runs in your browser with nothing uploaded. The arithmetic is in the page, so it works offline once loaded and nothing you type is sent anywhere.

Key Features & Capabilities

What it does, and what it deliberately leaves to other pages.

Past midnight handled An end time earlier than the start is read as the next day, and the page says so instead of guessing silently.

Add and subtract too A time with days, hours, minutes and seconds added or taken off, with the day it lands on.

Decimal hours alongside Every answer in hours and minutes and in decimal hours, so the 7.45 for 7.75 mistake cannot happen.

Seconds kept exact The whole calculation is done in seconds, so nothing is rounded away on the way through.

The working shown Both times in seconds and the single subtraction, so the answer can be checked rather than trusted.

Nothing is uploaded It runs in this tab and keeps working offline.

About Time Durations

A time duration is the gap between two points on the clock, and it looks like the simplest arithmetic there is until the gap crosses midnight. From 09:00 to 17:30 is a subtraction anyone can do in their head. From 22:00 to 06:00 is the same subtraction and gives minus sixteen hours, which is wrong by twenty four. That single case is behind a large share of the wrong totals in hand built rota spreadsheets, and it is why this page adds a day of its own accord when the end time is earlier than the start, and prints a line saying that it has.

The second trap is the decimal hour. Payroll systems, invoices and project trackers usually want hours as a decimal, and 7 hours 45 minutes becomes 7.75 because 45 minutes is three quarters of an hour. Writing 7.45 instead is an easy slip and loses eighteen minutes a day, which over a month is most of a working day. There is no way to tell the two apart by looking at the number, so the only safe habit is to convert deliberately and to see both forms together, which is what the result panel here shows.

Adding and subtracting time is the same calculation turned round. A start time becomes a number of seconds, the amount is added or taken off, and the result is brought back into the 0 to 24 hour range while counting how many days were crossed. That counting is the part worth seeing: 22:45 plus eight hours fifteen is 07:00 the next day, and a page that shows only 07:00 has told you half the answer. The day shift is printed with every result for that reason.

What this page deliberately does not do is work in dates or follow a time zone through a clock change. The gap between two calendar dates belongs to the date difference calculator, a week of shifts with breaks and overtime belongs to the hours calculator, and a time that must survive daylight saving in a named zone belongs to the time zone converter. Keeping this page on plain clock arithmetic is what lets it stay exact to the second and honest about what it is answering.

Frequently Asked Questions

Night shifts, decimal hours and seconds.

Eight hours. The end time is earlier on the clock, so it falls on the next day, and this page adds that day automatically rather than returning a negative number.

7.75 hours. Minutes are divided by 60, so 45 minutes is 0.75 of an hour. Writing it as 7.45 is a common and expensive mistake.

Yes. Use the days box, or simply type the hours: 0 days 30 hours is accepted and the result shows which day it lands on.

Yes. The minute and second boxes accept any whole number, and the working shows what the page read that as.

Yes. The calculation is done in seconds throughout, so a gap of 1:23:45 is exact. If your times have no seconds the answer simply ends in zero.

This page does plain clock arithmetic, which is what rotas and timesheets use, so a shift from 22:00 to 06:00 is always eight hours here. Real elapsed time on a clock change day is an hour more or less, and the time zone converter handles that case.

No. The arithmetic runs in your browser, so nothing you type leaves the page and it works offline.