Time calculator, add and subtract time.

A time calculator adds and subtracts hours, minutes and seconds, which is awkward by hand because the numbers carry at 60, not at 10. This one does it in three ways. It adds and subtracts as many durations as you like, it finds a clock time after adding or taking away a duration, and it reads a sum you type. The answer comes out as words, as h:mm:ss, in decimal hours, in total minutes and in total seconds.

How to add and subtract time in rows

1. Open Add and subtract. Each row has Days, Hours, Min and Sec boxes. Type what you have. An empty box counts as 0.
2. Press the + at the start of a row to turn it into a minus when that time should be taken away.
3. Press Add a row for more. The x at the end of a row removes it, and Clear rows starts again.
4. To scale the total, pick Multiply by or Divide by under Then and type a number.
5. Read the big card. The cards below give h:mm:ss, decimal hours, total minutes, total seconds, total days and a duration code. Step by step shows the running total after each row.

Carrying over 60: three worked examples

Add 2 hours 45 minutes and 1 hour 30 minutes. Minutes first: 45 + 30 = 75, which is 1 hour 15 minutes. Hours: 2 + 1 = 3. Add the carried hour and you get 4 hours 15 minutes, or 4:15.

Add 8 hours 50 minutes and 5 hours 25 minutes. Minutes: 50 + 25 = 75, so 1 hour 15 minutes. Hours: 8 + 5 + 1 = 14. The answer is 14 hours 15 minutes, which is 14:15:00.

Subtract 3:45 from 10:00. Take 10:00 as 9 hours 60 minutes, so the minutes are 60 - 45 = 15 and the hours are 9 - 3 = 6. The answer is 6:15.

Multiplying works on the whole time. 1 hour 36 minutes is 96 minutes, times 3 is 288 minutes, which is 4 hours 48 minutes. Dividing 5 hours by 4 is 300 minutes divided by 4, which is 75 minutes, or 1 hour 15 minutes.

How to find a clock time plus or minus a duration

1. Open Clock time and set the Start time, or press Now for the time on your device.
2. Choose Add or Subtract and type the Days, Hours, Minutes or Seconds.
3. Optionally pick a Start date. The result then names the date it lands on.

Example: a night flight leaves at 10:45 PM and lasts 5 hours 20 minutes. 22:45 plus 5:20 is 28:05, and 28:05 is 24:00 plus 4:05. So you land at 4:05 AM, the next day. Going the other way, 9:30 PM minus 14 hours 45 minutes is 21:30 minus 14:45, which is 6:45 AM the same day.

This tab moves the hands of the clock only. It does not look at time zones or daylight saving. If a clock change falls in between, use the date calculator with Include a time of day, or the time zone converter.

Typing a sum

The Type a sum tab reads one line or one time per line. It understands 2:45, 2h 45m, 90 min and 45s. It also understands days: 1d 2h. Put x or / with a plain number to scale a time, and a time divided by a time gives a plain number: 3h / 45m is 4. Two times cannot be multiplied together, and a bare number cannot be added to a time, because the page will not guess whether 45 means minutes or hours.

Try 1d 2h 3m 4s + 4h 5s - 2030s. In seconds that is 93,784 + 14,405 - 2,030 = 106,159. Divide by 86,400 for 1 day and 19,759 seconds are left, which is 5 hours (18,000), 29 minutes (1,740) and 19 seconds. The answer is 1 day, 5 hours, 29 minutes and 19 seconds.

Minutes as decimal hours

Pay and invoices usually need decimal hours. The rule is minutes divided by 60. 4 hours 15 minutes is 4.25 hours, and 7 hours 50 minutes is 7.8333 hours.

Common problems

• A time does not add up as expected. Check that 1:30 means 1 hour 30 minutes, not 1.30 hours. In the boxes you can use 1.5 hours instead.
• A negative answer. The total is below zero, so it reads "minus". Switch the order of the rows to get a positive time.
• A red message in Type a sum. It names the part it could not read. Add the unit, or put a sign between the times.
• Seconds with a fraction. Dividing can leave a fraction of a second. The page keeps three decimals and says so.

For hours between two clock times, a weekly time card, overtime and pay, use the hours calculator. To convert a 24 hour time, see the military time converter.