Time Duration Calculator

How it works

Every duration is first turned into a single number of seconds: 60 seconds in a minute, 60 minutes in an hour, 24 hours in a day. Adding, subtracting, multiplying and dividing then work on that one number, and the answer is split back into days, hours, minutes and seconds.

You can type a duration however it comes: 90 minutes, or 1 hour 30 minutes, or 5,400 seconds all mean the same thing, and overflowing fields (75 minutes, 30 hours) are carried over automatically.

Decimal hours are what timesheets and payroll use: 7 hours 45 minutes is 7.75 hours, because 45 ÷ 60 = 0.75. The two conversion operations go between the h:mm:ss form and that decimal form in either direction.

The h:mm:ss result counts every hour, so one day and two hours shows as 26:00:00. The days/hours/minutes/seconds fields show the same duration with the days taken out.

Formula

seconds = days × 86,400 + hours × 3,600 + minutes × 60 + seconds
A + B, A − B, A × factor, A ÷ factor      (all in seconds)
days = ⌊s ÷ 86,400⌋   hours = ⌊(s mod 86,400) ÷ 3,600⌋
minutes = ⌊(s mod 3,600) ÷ 60⌋   seconds = s mod 60
decimal hours = h + m ÷ 60 + s ÷ 3,600

Example

2 h 30 min plus 1 h 45 min 30 s: 9,000 s + 6,330 s = 15,330 s, which is 4:15:30, or 4.2583 decimal hours.

7 h 30 min in decimal hours is 7 + 30 ÷ 60 = 7.5 h. Going the other way, 2.5 decimal hours is 2:30:00.

One day divided by 3 is 86,400 ÷ 3 = 28,800 s, which is 8:00:00.

Assumptions and limitations

• A day is exactly 24 hours (86,400 s). Daylight-saving changes, leap seconds and calendar dates are not involved; use the date difference calculator for dates.
• Subtracting a longer duration from a shorter one gives a negative result, shown with a minus sign in front of the h:mm:ss form and as negative total seconds and decimal hours. The day/hour/minute/second fields show its size.
• Seconds are kept to the microsecond and displayed to two decimal places; the other fields are whole numbers.

Frequently asked questions