Time Converter

How do you convert time units?

To convert time units, multiply by the starting unit's length in seconds, then divide by the target unit's length in seconds. Every time unit has a fixed length in seconds, so the method never changes. A minute is 60 s, an hour is 3,600 s, a day is 86,400 s and a week is 604,800 s.

A worked example

To convert 2.5 days to minutes: 2.5 × 86,400 = 216,000 s, then 216,000 ÷ 60 = 3,600 minutes. For neighboring units a single factor is quicker. Divide seconds by 60 to get minutes with the seconds to minutes converter, divide minutes by 60 to get hours, as in the minutes to hours converter, multiply hours by 60 to get minutes with the hours to minutes converter, and divide days by 7 to get weeks with the days to weeks converter.

Decimal hours versus hours and minutes

Timesheets and payroll systems often record time as decimal hours, which is a common source of mistakes. 1.75 hours is 1 hour 45 minutes, not 1 hour 75 minutes, because 0.75 × 60 = 45. Going the other way, 7 hours 20 minutes is 7 + 20 ÷ 60 = 7.3333 hours. A handy set to memorize: 0.25 h = 15 min, 0.5 h = 30 min, 0.1 h = 6 min.

Calendar months and years versus averages

Real calendar months run from 28 to 31 days, and a calendar year has either 365 or 366 days. A converter cannot know which month or year you mean, so it uses the Gregorian averages. The Gregorian calendar has 97 leap years in every 400-year cycle, which gives 365.2425 days per year, and dividing by 12 gives 30.436875 days per month. These averages are ideal for long-range estimates such as loan terms or ages. For an exact count between two specific dates, use the date calculator instead.

What is the SI unit of time, and how is the second defined?

The second (s) is the SI base unit of time, defined by fixing the frequency of a hyperfine transition in the cesium-133 atom at exactly 9,192,631,770 hertz. In plain terms, one second is the time taken by 9,192,631,770 cycles of that radiation. The BIPM SI Brochure (9th edition, 2019) states the definition this way, and the atomic second has been in use since 1967.

Before atomic clocks, the second was a fraction of the day: 1/86,400 of a mean solar day. Earth's rotation is not perfectly steady, so a day measured by the sun can differ from 86,400 atomic seconds by a few milliseconds, which is the gap leap seconds were introduced to close. Today, International Atomic Time (TAI) counts atomic seconds without interruption, and Coordinated Universal Time (UTC), the basis of every civil time zone, is kept within a second of Earth's rotation.

The minute, hour and day are not SI units, but the SI Brochure accepts them for use with the SI and fixes them exactly: 1 min = 60 s, 1 h = 3,600 s and 1 d = 86,400 s. Weeks follow from days, while months and years vary, which is why this converter uses Gregorian averages for them. Because frequency is cycles per second, the hertz is the inverse of the second; the frequency converter works with it directly.

How do you convert seconds to hours, minutes and seconds?

Divide the seconds by 3,600 for whole hours, divide what is left by 60 for whole minutes, and the remainder is seconds: 10,000 seconds is 2 hours 46 minutes 40 seconds. Working in the other direction, multiply hours by 3,600 and minutes by 60 and add everything up, so a race time of 3:45:30 is 13,530 seconds.

1. 10,000 ÷ 3,600 = 2.7778, so there are 2 whole hours (7,200 s).
2. 10,000 − 7,200 = 2,800 s left; 2,800 ÷ 60 = 46.6667, so 46 whole minutes (2,760 s).
3. 2,800 − 2,760 = 40 seconds remain.

For a simple minutes-only answer, the seconds to minutes converter divides by 60, and 135 minutes is 2.25 hours in the minutes to hours converter. Spreadsheets such as Excel and Google Sheets store times as fractions of a day, so dividing a cell of seconds by 86,400 and formatting it as [h]:mm:ss displays hours, minutes and seconds.

In data and software, ISO 8601 writes durations with letters: PT2H46M40S means 2 hours 46 minutes 40 seconds, and P1DT12H means one day and 12 hours. For a duration between two calendar dates rather than a count of units, use the date calculator.

Where is each time unit used?

Seconds and their fractions run science and computing, minutes and hours run the working day, and days, weeks, months and years run calendars, contracts and plans. Each scale has its own conventions.

• Nanoseconds and microseconds: computer processors, memory latency, network timing and physics experiments, where events happen far faster than a human can notice.
• Milliseconds: web page load times, audio and video latency, reaction-time tests and sports timing to the thousandth of a second.
• Seconds: the SI base unit, used in science, engineering and anywhere precise timing matters. Since 1967 the second has been defined by a transition of the cesium-133 atom, and the frequency converter covers its inverse, the hertz.
• Minutes and hours: work shifts, payroll, travel times, cooking and appointments around the world.
• Days and weeks: project schedules, pregnancy tracking, shipping estimates and ISO 8601 week numbering used in business planning, especially in Europe.
• Months and years: contracts, subscriptions, loan terms, warranties and ages. Finance often uses its own conventions, such as a 360-day year, so check the terms before relying on an average.

How do leap years and leap seconds work?

A year is a leap year if it is divisible by 4, except century years, which must also be divisible by 400. That is why 2000 was a leap year and 1900 was not. The rule keeps the calendar aligned with the seasons and produces the 365.2425-day average used above. Separately, leap seconds have occasionally been added to Coordinated Universal Time (UTC) to keep it close to Earth's rotation; in 2022 the General Conference on Weights and Measures voted to let UTC and Earth-rotation time drift further apart by 2035, which effectively ends leap seconds. Leap seconds do not change unit conversions: a minute in this converter is always exactly 60 seconds.

Converting a duration is different from converting a clock time. Three hours is always 180 minutes, but 3:00 pm in New York is a different clock time in London or Tokyo. For that, use the time zone converter.