Calculators

Time Calculator

한국어

Add durations together

Duration 1
Duration 2

Enter hours, minutes or seconds to see the total.

How it is calculated

total (seconds) = Σ (hours × 3600 + minutes × 60 + seconds)
time between (seconds) = end − start (+ 86,400 if the next day)
  • Everything is converted to seconds, added, then rebuilt into hours, minutes and seconds. Entering 90 minutes is fine — it comes back as 1 hour 30 minutes.
  • Empty boxes count as 0. A row left completely empty is skipped rather than treated as zero.
  • Negative amounts are rejected.
  • Crossing midnight is never assumed. If the end time is earlier than the start time and the "next day" option is off, the calculator stops and asks you to turn it on. Only you can know whether 22:00 to 06:00 means eight hours or minus sixteen.
  • With "next day" on, the same time on both sides is a full 24 hours (00:00 → 00:00 = 24 hours).
  • Times use the 24-hour HH:MM format. The calculation also accepts HH:MM:SS where the browser's time control permits seconds.
  • Fractional entries are allowed and are not rounded away before adding: 0.5 hours is 30 minutes. The total is rounded to the nearest second only at the end.
  • You can add up to 10 durations. The last remaining row cannot be removed.

Examples

1. Adding up study time

1 hour 45 minutes + 30 minutes 30 seconds + 2 hours 5 minutes 45 seconds = 4 hours 21 minutes 15 seconds, or 4.3542 hours as a decimal.

2. A day shift

Starting at 09:00 and finishing at 18:30 is 9 hours 30 minutes (9.5 hours). Break time has to be subtracted separately.

3. A night shift past midnight

22:30 to 06:15 with "next day" turned on is 7 hours 45 minutes. Leave the option off and the calculator will not guess — it explains what to do instead.

4. Midnight boundaries

23:30 → 00:30 the next day is 1 hour. 00:00 → 23:59 on the same day is 23 hours 59 minutes.

5. Seconds carrying over

45 seconds + 30 seconds is 1 minute 15 seconds, not 75 seconds. 60 seconds make a minute, and 60 minutes make an hour.

Please note

Pay and overtime depend on break rules, night or overtime premiums and your employer's policy. This tool only measures the length of time.

Privacy

Everything is calculated in your browser. Nothing you type is sent anywhere or stored, and refreshing the page clears it. Read the Privacy Policy for details.

Add several durations together, or measure how long it is between two clock times.

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