Time Converter
Convert between different time units quickly and accurately.
Result
0.017
min
Common Time Conversions
1 hour = 3600 seconds
1 day = 24 hours
1 week = 7 days
1 year = 365 days
Frequently Asked Questions
How many seconds are in an hour?
There are 3600 seconds in one hour (60 minutes × 60 seconds). This is useful for timing calculations and scientific work.
How do I convert days to hours?
To convert days to hours, multiply by 24. For example, 3 days = 3 × 24 = 72 hours.
How many weeks are in a year?
There are approximately 52.14 weeks in a year (365 days ÷ 7). This is commonly used for project planning and goal setting.
Overview
Time is the most familiar and the most layered of the basic measurements. Every other SI unit is defined in terms of physical constants, but the second is now defined by atomic clocks as exactly 9,192,631,770 cycles of the radiation from a cesium-133 atom, replacing the older definition based on the length of the Earth's day. The time-converter on this page handles the units that come up in computing, scheduling, science, and history: milliseconds, seconds, minutes, hours, days, weeks, months, years, and decades.
The smaller units scale cleanly: 1 second = 1,000 milliseconds, 1 minute = 60 seconds, 1 hour = 60 minutes = 3,600 seconds, and 1 day = 24 hours = 86,400 seconds. Above a day the relationships get messier. A week is 7 days, but a month is 28 to 31 days, and a year is 365 days, 366 in a leap year. The Julian year, used in astronomy, is exactly 365.25 days; the tropical year, which marks the seasons, is about 365.2422 days. A decade is 10 years, a century is 100, and a millennium is 1,000.
Leap years are the calendar's way of keeping the calendar year close to the tropical year. The Gregorian rule, in use worldwide for civil purposes, adds a leap day in any year divisible by 4, except for years divisible by 100, unless also divisible by 400. That is why 2000 was a leap year (divisible by 400) but 1900 was not (divisible by 100 but not 400), and why 2024 was a leap year. The Gregorian calendar has 97 leap days every 400 years, for an average year of 365.2425 days, very close to the tropical year.
Different cultures and traditions have other calendars that show up in historical and religious contexts. The Islamic (Hijri) calendar is lunar, with 12 months of 29 or 30 days for a year of 354 or 355 days, about 11 days shorter than the solar year. The Hebrew calendar is lunisolar, with 12 or 13 months and a 19-year Metonic cycle that adds 7 leap months. The Julian calendar, used before the Gregorian reform in 1582, has a year of 365.25 days and now drifts by about 13 days relative to the Gregorian calendar. The converter on this page uses the standard Gregorian year of 365.2425 days for month and year conversions.
For practical use, type a value in any field and the others update. A work day of 8 hours is 28,800 seconds or 480 minutes; a 30-year mortgage is 360 months or 9,131 days (with leap years). The form is most useful for unit math, not for calendar arithmetic, where specific dates need a separate date calculator.
How to use
- Type a value in any of the supported fields: ms, s, min, h, day, week, month, year, or decade.
- Read the matching values in the other units, updated automatically.
- Note that month and year conversions use the Gregorian average of 30.4368 days per month and 365.2425 days per year.
- For specific date arithmetic, use the date calculator, which handles leap years and calendar offsets.
Formula
Interpreting your results
Months and years vary in length, so conversions use calendar averages: 30.4368 days per month and 365.2425 days per Gregorian year. For specific periods, the right tool is a date calculator that counts actual days. The Islamic year is 354 or 355 days, and a year in the Hebrew calendar is 353 to 385 days depending on whether a leap month is added, so non-Gregorian year conversions are not directly comparable to the values shown here.