Time Calculator

Add and subtract hours, minutes, and seconds across up to 20 rows. This time calculator gives the total as HH:MM:SS, in decimal hours, and in minutes.

Updated
Runs in your browser. Your data is not uploaded.
Times to add or subtract (empty fields count as 0)
Total time
–

How to use the Time Calculator

  1. Enter days, hours, minutes, and seconds in the first row. Empty fields count as 0.
  2. In the next row, choose + or − and enter the time to add or subtract. Press Add row for more entries, up to 20.
  3. Press Calculate. The total appears as HH:MM:SS, with decimal hours, total minutes, and total seconds underneath.

How it works

Every row is turned into seconds. The rows are added or subtracted, and the total is split back into days, hours, minutes, and seconds.

rowSeconds = D × 86400 + H × 3600 + M × 60 + S
total = Σ (sign × rowSeconds)
  • D, H, M, S: the days, hours, minutes, and seconds in one row
  • sign: +1 for a row you add, −1 for a row you subtract
  • total: the result in seconds. Its absolute value is split into days, hours, minutes, and seconds, and a minus sign is added when it is negative.

Decimal hours are the total seconds divided by 3,600, shown to 4 decimal places.

Examples

  • 2:45:30 + 1:30:45 = 4:16:15. That is 4.2708 hours, 256.25 minutes, or 15,375 seconds.
  • 8:00:00 − 2:45:30 = 5:14:30.
  • A row of 0 hours and 90 minutes is normalized to 1:30:00.

Why you can't add time like ordinary numbers

Time counts in sixties, not tens, so a normal calculator gives the wrong answer. 1:30 plus 1:45 is 3:15. Type 1.30 + 1.45 into a standard calculator and you get 2.75, which reads like 2 hours and 75 minutes.

Decimal hours are something else again. 1:30 is 1.5 hours, because 30 minutes is half an hour. Payroll and invoicing systems usually want decimal hours, while schedules and video lengths use hours and minutes. The calculator shows both, so you can paste whichever format the other system expects.

Common uses

  • Adding up the lengths of video or audio clips
  • Totalling time spent on tasks for an invoice
  • Subtracting breaks from a block of time
  • Adding lap or split times

Limitations

  • Each field takes a whole number from 0 to 99,999. Decimals and negative numbers are rejected. To take time away, use the − operation.
  • Minutes and seconds above 59 are allowed and carried over automatically.
  • If you subtract more than you add, the total is negative and shown with a minus sign.
  • This tool adds up amounts of time, not clock times. For the gap between 09:15 and 17:40, use the time duration calculator.

Frequently asked questions

How do I add hours and minutes together?

Add seconds, then minutes, then hours. Every 60 seconds carries 1 minute, and every 60 minutes carries 1 hour. The calculator does this for any number of rows.

What happens if I enter more than 59 minutes?

The extra minutes are converted into hours automatically. For example, 90 minutes becomes 1 hour 30 minutes.

Can the result be negative?

Yes. If you subtract more time than you add, the total is shown with a minus sign.

How do I convert the total to decimal hours?

Divide the minutes by 60 and the seconds by 3,600, then add them to the hours. The decimal value is shown under the main result.

Often used together with the Time Calculator.