Time Unit Converter

How to use the time unit converter

1. Enter a number in Value and choose its unit in From, anything from nanoseconds to millennia.
2. Choose the unit you want in To. The answer appears at once, and the table underneath lists the same duration in every unit.
3. For longer durations, the line under the result also breaks the time into years, days, hours, minutes and seconds, so 100,000 seconds reads as 1 day 3 hours 46 minutes 40 seconds.

Use ⇄ to reverse the conversion, and the decimal-places menu to show more or fewer digits.

The units and where they come from

Why months and years are not exact

Seconds, minutes, hours, days and weeks are fixed. Months and years are not. A calendar month can have 28, 29, 30 or 31 days, and a calendar year has 365 or 366. A converter that turns "1 month" into a number of days therefore has to choose, and this one uses averages: a year is 365.25 days (the average of the Gregorian cycle over four years, ignoring the century rule) and a month is exactly one twelfth of that, or 30.4375 days.

The true Gregorian average is slightly shorter, at 365.2425 days, because years divisible by 100 are not leap years unless they are also divisible by 400. The difference is 0.0075 days a year, about 11 minutes, which only matters across centuries. For exact calendar spans between two real dates, use a date calculator instead of a unit converter.

1 year = 365.25 days = 8,766 hours = 525,960 minutes = 31,557,600 seconds 1 month = 365.25 ÷ 12 = 30.4375 days = 730.5 hours Seconds ÷ 3,600 = hours Hours × 60 = minutes Days × 24 = hours

Worked examples

• A 2.5-hour film in minutes: 2.5 × 60 = 150 minutes.
• A 40-hour working week in minutes: 40 × 60 = 2,400 minutes, or 144,000 seconds.
• 86,400 seconds in days: 86,400 ÷ 86,400 = exactly 1 day.
• An 80-year lifetime in hours: 80 × 8,766 = 701,280 hours, or roughly 29,220 days.
• A 5 ms network delay in seconds: 5 × 0.001 = 0.005 s, and in microseconds, 5,000 µs.
• 1 million seconds: 11 days 13 hours 46 minutes 40 seconds, which is why a "million seconds" feels so much shorter than a "billion seconds", which is about 31.7 years.

Handy reference points

For software work, remember that timestamps in milliseconds (JavaScript) are 1,000 times larger than those in seconds (Unix). A value near 1,700,000,000 is in seconds, and one near 1,700,000,000,000 is in milliseconds.

Time in computing and science

Computers and instruments use the small units. A modern processor executes an instruction in about a nanosecond (one billionth of a second); light travels about 30 centimetres in that time. A microsecond is a thousand nanoseconds and is the scale of fast sensor readings, while a millisecond is the scale of network delays and animation frames: a screen refreshing 60 times a second has about 16.7 ms per frame. Human reaction time is roughly 200 to 250 ms.

At the other end, geologists and historians use decades, centuries and millennia, and astronomers use the 365.25-day Julian year to define the light-year. If you need to find the time between two real dates rather than convert a duration, the date difference tool counts actual calendar days.

Accuracy and limits

Conversions between fixed units (seconds to weeks) are exact. Anything involving months, years, decades or centuries uses the average lengths described above, so it will not match the number of days on a real calendar. The tool ignores leap seconds, time zones and daylight saving changes. Very large or very small answers are shown in scientific notation when they would not fit on one line.

Frequently asked questions