How the time calculator works
Each row is read as an exact number of milliseconds, and the rows are added or subtracted in order. Nothing is rounded on the way, so ten rows of 0.1h come to exactly 1:00:00. The total is shown five ways: as h:mm:ss, in decimal hours, in decimal minutes, in seconds, and as days, hours and minutes.
What you can type
| You type | It means |
|---|---|
1:30:00 | 1 hour, 30 minutes, 0 seconds |
1:30 | 1 hour 30 minutes — or 1 minute 30 seconds if you switch Read 1:30 as to minutes : seconds |
90m | 90 minutes, which is 1:30:00 |
1h 30m | 1 hour 30 minutes |
1.5h | 1.5 hours, which is 1:30:00 |
45s | 45 seconds |
5400 | 5,400 seconds, which is 1:30:00 |
2 days 3 hours | 51 hours |
A worked example
Add 2:45:30 and 1:30:45, then subtract 0:20:15. In seconds that is 9,930 + 5,445 − 1,215 = 14,160, which is 3:56:00. Divide 14,160 by 3,600 for decimal hours (3.9333) and by 60 for decimal minutes (236).
If you subtract more than you add, the total goes negative and is shown with a leading minus sign: 30 minutes minus 1 hour is −0:30:00. That is handy for seeing how far you are under or over a target.
Tips for adding a list of times
- Put one time in each row and use + Add row for as many as you need. Rows you leave empty are ignored.
- Use the minus button for a break, a lap you want to take away, or a time you are counting down from.
- A row that cannot be read is marked and left out of the total, so a typo never turns into a wrong answer silently.
- Copy result copies the h:mm:ss total; Copy all formats copies every readout.
Date and time mode
Choose a start date and time, pick Add or Subtract, and enter days, hours, minutes and seconds. The result shows the date, the time and the day of the week. For example, start on Friday, October 2, 2026 at 2:00 p.m. and add 1 day, 8 hours and 30 minutes: the answer is Saturday, October 3, 2026 at 10:30 p.m.
Whole days move the calendar, so 2:00 p.m. plus one day is still 2:00 p.m. even if the clocks change in between. Hours, minutes and seconds are elapsed time, so adding 24 hours across a clock change gives a time one hour different on the clock. The page tells you when that happens.
Related tools
To find the hours between a start and an end time, use the hours calculator. To change units, use the time converter. To measure a duration instead of typing it, use the stopwatch. For the time until or since a date, try countdown to and time since.
Questions
How do I add hours and minutes together?
Type each time in its own row — 2:45 and 1:30, or 2h 45m and 1h 30m — and leave both on plus. The total updates as you type. Here it reads 4:15:00, because the minutes carry over: 45 + 30 = 75 minutes, which is 1 hour 15 minutes.
How do I subtract time?
Press the minus button on a row. 8:00 minus 1:15 leaves 6:45. If you subtract more than you have, the total goes negative and shows a minus sign. To subtract one clock time from another, such as 5:30 p.m. minus 9:15 a.m., use the hours calculator instead.
How do I convert 1.5 hours to hours and minutes?
Type 1.5h in a row. The total reads 1:30:00, which is 1 hour 30 minutes. The same works for any decimal: 2.25h is 2:15:00 and 0.75h is 0:45:00. By hand, multiply the part after the decimal point by 60 to get the minutes.
What does 1:30 mean — an hour and a half, or a minute and a half?
By default 1:30 is read as hours and minutes, so it means 1 hour 30 minutes. If you are adding lap or race times, change Read 1:30 as to minutes : seconds and it becomes 1 minute 30 seconds. Times with three parts, such as 1:30:00, are always hours, minutes, seconds.
How do I find the time 8 hours after a given time?
Switch to Date and time, choose the starting date and time, leave the operation on Add, and enter 8 in hours. The result shows the new date, time and weekday, so it handles crossing midnight. Choose Subtract to go back instead.
Can I add days, weeks or milliseconds?
Rows accept days, hours, minutes, seconds and milliseconds, such as 2 days 3 hours or 500ms. Weeks are not a unit here, so type 14 days for two weeks. In Date and time mode there are separate fields for days, hours, minutes and seconds.