Time calculator

This time calculator adds or subtracts a list of durations and finds the hours and minutes between two clock times. It handles overnight spans and base-60 math so 1.5 hours becomes 1:30, not 1:50.

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What this time calculator does

You can work with time in two ways here. The first mode adds or subtracts a list of durations. Type each one as 1:30, 90m, 2h 15m, or 5:00. The second mode finds the elapsed time between two clock times, such as 9:00 to 17:30. That answer is 8:30. If the end time is earlier than the start time, the calculator treats it as the next day. So 22:00 to 06:00 gives 8:00, not a negative number.

Both modes use base-60 arithmetic. That means minutes and seconds roll over at 60, not 100. This is the part that trips people up most often.

Why 1.5 hours is 1:30, not 1:50

An hour has 60 minutes. Half of 60 is 30. So 1.5 hours is 1 hour and 30 minutes, written 1:30. It is not 1:50. The decimal .5 means half, and half of an hour is 30 minutes.

The same rule applies to any decimal. To turn decimal hours into minutes, multiply the decimal part by 60. Here is a short table:

Decimal hours	Hours and minutes
1.5	1:30
7.5	7:30
0.75	0:45
2.25	2:15

To go the other way, divide the minutes by 60. So 7:30 becomes 7.5 hours because 30 divided by 60 is 0.5. And 0:45 becomes 0.75 hours because 45 divided by 60 is 0.75. This matters for timesheets. Many payroll systems want decimal hours, not hours and minutes. If you write 7:30 as 7.50, you are correct. If you write it as 7.30, you are shorting yourself by 12 minutes.

Adding and subtracting durations

You can type durations in several formats. A plain number like 5 means 5 seconds. The format 5:00 means 5 minutes and 0 seconds. The format 1:30:00 means 1 hour, 30 minutes, and 0 seconds. You can also use 90m for 90 minutes, 1h 30m for 1 hour and 30 minutes, or 2d 3h for 2 days and 3 hours.

When you add a list, the calculator carries over at 60. For example, add 45m and 30m. That is 75 minutes total. Since 75 is more than 60, you carry 1 hour and keep 15 minutes. The answer is 1:15.

Subtraction works the same way in reverse. If you subtract 50m from 1h 20m, you borrow 1 hour as 60 minutes. Then 80 minutes minus 50 minutes is 30 minutes. The answer is 0:30.

This mode is useful for building a schedule, adding up workout intervals, or totaling billable time from a list of short tasks.

Time between two clock times

This mode answers questions like "how many hours between 9:00 and 17:30?" The answer is 8:30. You can type clock times as 9:00, 9:00 am, 17:30, or 1730. The calculator reads all of them.

The overnight rule is simple. If the end time is earlier than the start time, the calculator adds 24 hours to the end time before subtracting. So 23:30 to 00:30 is 1:00. And 22:00 to 06:00 is 8:00. This is how shift workers and anyone tracking sleep or travel time gets a correct answer without doing mental math at midnight.

One thing to know: every day here is 24 hours. Daylight saving changes are not counted. So a day never has 23 or 25 hours in this calculator. That keeps the math predictable.

Worked example

Suppose you worked four shifts this week. Monday was 7:30. Tuesday was 8:15. Wednesday was 6:45. Thursday was 7:00. You want the total in decimal hours for a timesheet.

First, add the hours and minutes. 7:30 plus 8:15 is 15:45. Add 6:45 to get 22:30. Add 7:00 to get 29:30. So the total is 29 hours and 30 minutes.

Now convert to decimal. The 30 minutes is 30 divided by 60, which is 0.5. So the total is 29.5 hours. If you had written 29.30, you would be off by 12 minutes. That is the base-60 trap in one line.

You can also check the time between two clock times. From 9:00 to 17:30 is 8:30. That is 8.5 hours in decimal. A 30-minute unpaid lunch would make it 8:00, or 8.0 hours.

When to use each mode

Use add or subtract when you have a list of durations to total, such as workout intervals, study blocks, or billable tasks.
Use time between two times when you know the start and end clock times, such as a shift, a meeting, or a nap.
Use decimal hours when a timesheet or payroll form asks for a number like 7.5 instead of 7:30.

For related tools, try the date calculator for days between dates, the business days calculator for workdays only, or the stopwatch for live timing.

Frequently asked questions

How do I add hours and minutes together?

Type each duration in a format the calculator reads, such as 1:30, 90m, or 2h 15m. It adds them and carries over at 60. So 45m plus 30m becomes 1:15, not 0:75. The total shows in hours, minutes, and seconds.

Why is 1.5 hours 1:30 and not 1:50?

An hour has 60 minutes, so half an hour is 30 minutes. The decimal .5 means half. To convert decimal hours to minutes, multiply the decimal part by 60. That is why 1.5 hours is 1:30 and 7.5 hours is 7:30.

How do I calculate time between two times overnight?

Enter both clock times. If the end time is earlier than the start time, the calculator treats it as the next day and adds 24 hours. So 22:00 to 06:00 gives 8:00. This works for night shifts and sleep tracking.

How do I convert 7:30 to decimal hours for a timesheet?

Divide the minutes by 60. For 7:30, 30 divided by 60 is 0.5, so the decimal is 7.5 hours. For 0:45, 45 divided by 60 is 0.75. Writing 7.30 instead of 7.5 would be wrong by 12 minutes.

Does this calculator count daylight saving changes?

No. Every day is treated as 24 hours. Daylight saving shifts are not counted, so a day never has 23 or 25 hours here. That keeps the arithmetic simple and predictable for adding durations and finding elapsed time.