Time calculator
Add or subtract hours, minutes and seconds, or add up a whole list of times, with the working shown. Need the time between two clock times? Use the hours calculator.
Type each duration as h:mm:ss or h:mm. A plain number counts as minutes. Pick the minus sign on a row to take it away.
Pages made from this tool with your times in the address are not indexed by search engines. Nothing you type is sent to a server.
How to use it
- Pick a mode. Add or subtract time moves a clock time forward or back. Add up durations totals a list of times.
- In the first mode, type a clock time, choose add or subtract, then type the hours, minutes and seconds. In the second, type each row as h:mm:ss, and use the sign box to take a row away.
- Read the result. A time that passes midnight says so. A total shows as h:mm:ss, in decimal hours and in total minutes.
Worked examples
These six examples are worked out by the same code as the calculator above, so the answers always match.
| Question | Mode | Result |
|---|---|---|
| 2:45 plus 1:30 | Add up durations | 4:15:00, 4.25 h, 255 min |
| 10:20 PM plus 2 h 50 m | Add or subtract time | 1:10 AM the next day |
| 12:15 AM minus 45 min | Add or subtract time | 11:30 PM the previous day |
| 1:25:30 plus 0:45:00 plus 2:10:15 | Add up durations | 4:20:45, 4.35 h |
| 3:00:00 minus 0:45:30 | Add up durations, minus row | 2:14:30 |
| 2 h 15 m in minutes | Add up durations | 135 minutes |
Adding times by hand
Add the seconds first, then the minutes, then the hours. Whenever a column reaches 60, write the remainder and carry 1 into the next column.
Take 2:45 plus 1:30. The minutes are 45 plus 30, which is 75, so write 15 and carry one hour. The hours are 2 plus 1 plus the carried 1, which gives 4:15.
A list works the same way. Total every column, then carry once at the end. This is how the time adder gets 4:20:45 from 1:25:30, 0:45:00 and 2:10:15.
Subtracting times by hand
Subtract the seconds, then the minutes, then the hours. When the top number in a column is smaller, borrow 1 from the column to its left and add 60.
Take 3:00:00 minus 0:45:30. The seconds need a borrowed minute, so 60 minus 30 is 30. The minutes then need a borrowed hour, so 59 minus 45 is 14, and 2 hours are left, which gives 2:14:30.
Check a subtraction by adding the answer back to the number you took away. If you get the first number again, the sum is right.
Hours and minutes to decimal
A minute is one sixtieth of an hour. Divide the minutes by 60 and add the result to the hours, so 4 hours 15 minutes is 4.25 hours.
The chart shows the common steps. Use it to turn a time card entry into the decimal figure a pay system wants, or to go the other way.
When a result passes midnight
A clock only counts to 24 hours. When an addition runs past midnight, the calculator wraps the time round and tells you which day it landed on.
Add 2 hours 50 minutes to 10:20 PM and you reach 1:10 AM the next day. Take 45 minutes from 12:15 AM and you reach 11:30 PM the previous day.
For a change of more than a day, the note gives the number of days, such as 2 days later. The time shown is always the time on the clock.
12 hour and 24 hour time
Type times either way. The calculator reads 5:30 PM and 17:30 as the same moment, and it accepts short forms such as 5p and 1730.
The radio buttons change only how the answer is shown. Use the 24 hour display for rotas and logs, where AM and PM can cause slips.
In the adder, times are lengths and not clock times. A row of 25:00 is fine, because 25 hours is a valid length.
Where the time adder helps
Adding up times is a daily job for many people. It covers a week of shifts, a list of tracks, the legs of a trip or a set of lessons.
Type one row for each item and read the total. Add a row with the plus button, and remove one with its remove button.
Use a minus row for a break or a gap. A shift of 8:30:00 with a minus row of 0:30:00 leaves 8:00:00.
Questions people ask
How do I add times together?
Add the seconds, then the minutes, then the hours. When a column reaches 60, write the remainder and carry 1 to the next column. The time adder does this and shows its working.
What is 2:45 plus 1:30?
2:45 plus 1:30 is 4:15, which is 4 hours 15 minutes. In decimal hours that is 4.25, and in total minutes it is 255.
How many minutes is 2 hours 15 minutes?
It is 135 minutes. Multiply the 2 hours by 60 to get 120, then add the 15 minutes.
How do I subtract time?
Subtract the seconds, then the minutes, then the hours, and borrow 1 from the next column when you need it. To take time from a clock time, use the first mode and pick subtract.
Can I add up a whole week of times?
Yes. Switch to Add up durations and type one row per day, such as 8:30:00, using Add row for more. The total shows as h:mm:ss, in decimal hours and in minutes.
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Updated Wednesday, November 4, 2026.