Hours calculator

How to work out a duration by hand

Write both times on the 24 hour clock, so 5:40 PM becomes 17:40. Then subtract the minutes first and the hours second.

If the end minutes are smaller than the start minutes, borrow an hour. Add 60 to the end minutes, take 1 off the end hours, then subtract as before.

Take 9:40 to 17:15. The minutes are 15 minus 40, which is short, so use 75 minus 40, which is 35. The hours are 17 minus 1 minus 9, which is 7, so the answer is 7 hours 35 minutes.

Turning a duration into decimal hours

Divide the minutes by 60 and add them to the hours. A shift of 8 hours 25 minutes is 8 plus 25 divided by 60, which is 8.42 hours.

Pay systems and time sheets often want this form. Round to two places, and ask whether your employer rounds to the nearest quarter hour instead.

Durations that cross midnight

Leave the dates empty and the calculator assumes that an end time earlier than the start time falls on the next day. From 10:30 PM to 6:15 AM it shows 7 hours 45 minutes and says that it ends the next day.

By hand, add 24 hours to the end time before you subtract. Here 6:15 AM becomes 30:15, and 30:15 minus 22:30 is 7:45.

If the gap is longer than a day, enter both dates. The tool then counts the whole days and the clock difference. Equal times give zero, not 24 hours, so use an end date one day later for a full day.

Durations across a clock change

When clocks go forward, one hour of the night never happens. When they go back, one hour happens twice. A range that crosses a change is an hour shorter or longer than the clock suggests.

Enter dates and the tool uses the time zone of your device and the IANA time zone database. The headline figure is the real time that passed, and a note shows the figure on the clock as well.

The next changes are below, worked out from the same database as of Wednesday, November 4, 2026. Queensland, Western Australia and the Northern Territory do not change their clocks.

Clock duration, elapsed time and time hours

People search for the same sum under many names. Time duration, elapsed time, clock duration and the time between two times all mean the gap from a start to an end.

A time hours calculator and an hours and minutes calculator do the same job. They take two clock times and return the gap as hours and minutes.

The word duration is useful because it ends the confusion with a time of day. A time of day is a point on the clock, and a duration is a length.

Typing times in the form you use

The calculator reads many styles. You can type 9, 9:15, 0915, 9:15 AM, 9a, 21:15 or noon, and it takes the same meaning from each.

A bare number from 1 to 12 is read as that hour in the morning unless you add pm. Use the 24 hour clock when you want no doubt at all.

The radio buttons choose how the answer shows start and end times. They change the display only, never the length of the duration.

Using the answer for pay, billing and study

Decimal hours are the form that most pay and billing systems want. A shift of 7 hours 45 minutes is 7.75 hours, and the calculator shows both forms side by side.

The total minutes figure suits lessons, calls and parking, which are charged by the minute. Divide it by 60 if you want to see it in hours again.

Remember that the answer is the whole span. Take off any unpaid break yourself, for example 30 minutes for lunch, before you copy the figure.

Two dates and two times

Fill in both dates when the start and the end are on different days. A job that begins at 8 PM on Monday and ends at 7 AM on Wednesday needs the dates to give 35 hours.

The tool counts every whole day in between, then adds the clock difference. A note appears when the range crosses a change of clocks in your time zone.

If you put the later date first, the tool swaps the two and says so. That keeps the answer positive and easy to read.