How the conversion works
Every unit is a fixed number of seconds, so a conversion is one multiplication and one division: value × (seconds in the unit you have) ÷ (seconds in the unit you want). Type in any box and the others update. Very small and very large answers switch to powers of ten, such as 3.168808781×10−17, instead of a long run of zeros.
Useful equivalences
| Unit | Equals |
|---|---|
| 1 millisecond | 0.001 s = 1,000 microseconds |
| 1 second | 1,000 ms = 1,000,000 µs = 1,000,000,000 ns |
| 1 minute | 60 s |
| 1 hour | 60 min = 3,600 s |
| 1 day | 24 h = 1,440 min = 86,400 s |
| 1 week | 7 d = 168 h = 10,080 min = 604,800 s |
| 1 Julian year (365.25 days) | 8,766 h = 525,960 min = 31,557,600 s |
| 0.25 hour | 15 min |
| 0.1 hour | 6 min |
| 0.01 hour | 36 s |
| 0.5 minute | 30 s |
| 0.01 minute | 0.6 s |
Which year is it?
Years here are Julian years of 365.25 days, which is 31,557,600 seconds. A calendar year is 365 days (31,536,000 s) or 366 in a leap year (31,622,400 s), so a conversion to or from years is always an average. Months are left out for the same reason: they run from 28 to 31 days.
Clock time and decimals
A clock time such as 1:42:30 and a decimal such as 1.7083 hours are two ways to write the same duration. Add the hours, the minutes ÷ 60 and the seconds ÷ 3,600: 1 + 42 ÷ 60 + 30 ÷ 3,600 = 1.7083 hours, which is 102.5 minutes. Going back, 2.75 hours is 2 hours plus 0.75 × 60 = 45 minutes, or 2:45:00.
A common slip is reading 7:40 as 7.40 hours. Minutes run to 60, so 40 minutes is 40 ÷ 60 = 0.6667 of an hour and 7:40 is 7.6667 hours. Decimal minutes work the same way: 0.45 minute × 60 = 27 seconds, and 3 minutes 27 seconds is 3 + 27 ÷ 60 = 3.45 minutes.
For a worked unit conversion: 3,725 seconds ÷ 3,600 = 1.0347 hours, and as a clock time it is 1:02:05, because 3,600 + 120 + 5 = 3,725. Time-study work often uses decimal minutes; see decimal minutes explained and the time study stopwatch. To add or subtract durations, use the time calculator.
Questions
How many seconds are in a year?
A Julian year of 365.25 days is 31,557,600 seconds. A common year of 365 days is 31,536,000 seconds and a leap year of 366 days is 31,622,400. The converter uses the Julian figure so that years convert the same way every time.
How do I convert minutes to hours?
Divide by 60. 90 minutes ÷ 60 = 1.5 hours. For hours and minutes, keep the whole hours and use the remainder as minutes: 135 minutes is 2 hours 15 minutes, or 2.25 hours in decimal.
How do I convert hh:mm:ss to decimal hours?
Add the hours, the minutes divided by 60 and the seconds divided by 3,600. For 1:45:30 that is 1 + 0.75 + 0.008333 = 1.758333 hours. The clock-to-decimal converter also shows decimal minutes (105.5) and seconds (6,330).
How do I convert decimal minutes to seconds?
Multiply by 60. 0.45 minutes is 27 seconds, and 3.45 minutes is 207 seconds, or 3:27. Going back, divide the seconds by 60: 207 ÷ 60 = 3.45 minutes.
How many milliseconds are in a second?
1,000. A millisecond is a thousandth of a second, a microsecond a millionth and a nanosecond a billionth, so 1 s = 1,000 ms = 1,000,000 µs = 1,000,000,000 ns.
Why is 7:40 not 7.40 hours?
Minutes run to 60, not 100. Forty minutes is 40 ÷ 60 = 0.6667 of an hour, so 7:40 is 7.6667 hours. Writing 7.40 hours would mean 7 hours and 24 minutes, because 0.4 × 60 = 24.