Time Unit Converter: Seconds, Minutes, Hours, Days, Weeks, Months and Years

How to use this tool

Type a value, pick the unit it is in and the unit you want, and the answer sits in the dark panel with the same time broken into whole units next to it, so 100 hours reads as 4.17 days and as 4 days and 4 hours in the same glance. The cards underneath show the value in all ten units at once, plus hours and minutes and a spelled out breakdown from the largest unit down; tap any card to copy it. Swap reverses the two units and carries the result across, and the decimal places control applies everywhere on the page.

The two boxes below the units are the ones people skip and then argue about. Every factor from milliseconds up to weeks is fixed by definition, but a month and a year are not, so the converter tells you which length it is using and lets you change it. The default year is the 365 day calendar year, which is what most answers online assume; switch to 366 for a leap year, to 365.25 for the astronomical average, or to 365.2425 for the true Gregorian mean. The month defaults to one twelfth of the year, 30.4167 days, with 28, 29, 30 and 31 available when you mean a specific month.

The green note under the cards traces the factor step by step, for instance 1 week = 7 × 24 = 168 hours, and the amber note appears whenever a month or year is involved to say exactly what was assumed. The calendar check box takes any year and reports its days, its 52 weeks and 1 or 2 days, how many ISO weeks it has, whether it is a leap year, and for the current year which day and week you are in and how many hours are left.

Every export carries the value you entered and nothing else. Copy link gives an address that reopens the converter on the same value and units, with the year and month settings included if you changed them, and every chip and table row is a link with its own address too.

What the conversion is doing

Every value is turned into seconds first, then into the unit you asked for. A minute is 60 seconds, an hour 3,600, a day 86,400 and a week 604,800, and those four numbers are definitions rather than measurements: the second is the SI base unit, fixed by the caesium transition, and the minute, hour, day and week are counted multiples of it. Dividing one factor by another gives the factor between any two of those units, so 1 week ÷ 1 hour is 604,800 ÷ 3,600 = 168, and that is the whole calculation. Nothing is rounded until the answer is displayed.

Months and years break the pattern because the calendar does not contain a fixed one. A year is 365 or 366 days depending on which year, and a month is 28, 29, 30 or 31 days depending on which month. Any converter that returns a single number for hours in a year has picked a convention, usually without saying so. This one states the convention on every result and puts the four sensible choices in a drop down: the common year, the leap year, the Julian average of 365.25 that astronomers and many legal definitions use, and the Gregorian mean of 365.2425 that the civil calendar actually delivers over its 400 year cycle. The differences are small in hours, 8,760 against 8,784, 8,766 and 8,765.82, and they matter whenever the number is multiplied by something large, such as a wage or a power rating.

Decades and centuries are ten and a hundred of whichever year you chose. Milliseconds are a thousandth of a second and are on the page because timing logs, sleep functions and video frame arithmetic all produce them.

Why a year is not 52 weeks

Fifty two weeks is 364 days. A common year has one day more and a leap year two, which is why 1 January was a Wednesday in 2025, a Thursday in 2026 and will be a Friday in 2027: the extra day shifts every date one weekday forward, and a leap year shifts the dates after February by two. Divide 365 by 7 and you get 52.142857, the figure the converter shows, but the fraction is a leftover day, not a fraction of a week, and it is the reason a weekly payroll has 53 paydays in some years and why a 4 week budget cycle drifts a day a year against the calendar.

The ISO 8601 week standard, which is what week numbers on planners and in spreadsheets follow, counts whole weeks starting on Monday and assigns each week to the year that holds its Thursday. Under that rule a year has 52 weeks or 53, never a fraction. A year gets 53 when it starts on a Thursday, or when a leap year starts on a Wednesday; 2026 is one, and so are 2032, 2037, 2043 and 2048, which is 71 years in every 400. The calendar check on the tool tells you which kind any year is, and the date duration calculator linked below counts the real weeks between two dates when that is what you need.

The three average years exist because the calendar corrects itself in steps. Adding a leap day every four years gives the Julian average of 365.25 days, which is slightly too long, so the Gregorian reform drops three leap days in every 400 years: century years are only leap years if divisible by 400, so 1900 was not and 2000 was. That leaves 97 leap days in 400 years, an average of 365.2425 days, and a cycle of 146,097 days that happens to be exactly 20,871 weeks, so the calendar repeats weekday for weekday every four centuries. The true tropical year is about 365.2422 days, so even the Gregorian year runs long by roughly 27 seconds, an error that takes over three thousand years to add up to a day.

Months, the unit with no length

A month is whatever the calendar says it is, 28 to 31 days, so any conversion into or out of months is an average unless you name the month. Twelve months make a year, so the natural average is one twelfth of a year: 30.4167 days for a 365 day year, 30.4375 for the Julian year and 30.4369 for the Gregorian mean. In hours the same month is 730, and the real range is 672 to 744.

The trap is treating a month as four weeks. Four weeks is 28 days, and only February in a common year is that short. Twelve weeks is 84 days, which is 2.76 months, not three; 40 weeks is 280 days, about 9.2 months, which is why a pregnancy is quoted as nine months and forty weeks at the same time; and thirteen periods of four weeks make 364 days, a day short of the year. Six months is 182.5 days on the average month, 26 weeks and a day, so a contract quoted as six months and one quoted as 26 weeks are not quite the same length. When a deadline is in months, count it on the calendar rather than converting.

Hours, minutes and decimal time

Hours to minutes is multiplication by 60, and it is the single most searched conversion on this page because of what happens to the fraction. 1.5 hours is 90 minutes, not 1 hour 50, because the 0.5 is half of 60. The converter shows both forms side by side, the decimal and the hours and minutes, so 2.75 hours appears as 165 minutes and as 2:45, and 100 minutes appears as 1.67 hours and as 1:40.

Timesheets and billing run on decimal hours, and the rule is the one used above: keep the whole hours and divide the minutes by 60. An hour and twenty minutes is 1.33 hours, an hour and a half is 1.50, and the tenth of an hour that many payroll systems round to is six minutes, so 1:20 rounds to 1.3 and 1:25 to 1.4. Going the other way, multiply the fraction by 60 and read the result as minutes. The hours and minutes card on the tool does this for any value up to a hundred days, and the whole units card carries on into days and weeks when the number is bigger than that.

A worked check you can repeat on paper

Start with the default, one year into weeks. A common year is 365 days and a week is 7, so 365 ÷ 7 = 52 remainder 1: 52 weeks and 1 day, or 52.142857 weeks as a decimal. Switch the year to 366 and the remainder becomes 2, 52.2857 weeks; switch to 365.25 and it is 52.1786; switch to 365.2425 and it is 52.1775. The tool reports all four, so if yours differs, check which year you divided.

Now hours, minutes and seconds in the same year. 365 × 24 = 8,760 hours. Multiply by 60 for minutes, 525,600, and by 60 again for seconds, 31,536,000. A leap year adds one day, which is 24 hours, 1,440 minutes and 86,400 seconds, giving 8,784, 527,040 and 31,622,400. The Julian year of 365.25 days adds a quarter of that, six hours, and comes out at exactly 31,557,600 seconds, which is the value astronomers mean when they write a year in seconds.

Finally the two conversions people most often get wrong. 90 minutes into hours: 90 ÷ 60 = 1.5, and 0.5 of an hour is 30 minutes, so 1 hour 30, not 1 hour 50. A million seconds into days: 1,000,000 ÷ 86,400 = 11.574 days; the 11 whole days use 950,400 seconds, the remaining 49,600 seconds are 13 hours (46,800) plus 2,800 seconds, and 2,800 seconds are 46 minutes and 40 seconds. So a million seconds is 11 days, 13 hours, 46 minutes and 40 seconds, exactly what the whole units card shows.

Mistakes that catch people out

Treating a month as four weeks. It is 4.35 on average, and three months is 13 weeks, not 12. Anything planned in four week blocks loses a day a year and a whole month every 28 years.

Reading 1.5 hours as 1 hour 50. The decimal is a fraction of an hour, so 0.5 is 30 minutes and 0.25 is 15. The hours and minutes card exists so you never have to do this in your head.

Calling 52 weeks a year. It is 364 days. A weekly payroll or a weekly subscription bills 53 times in the years that hold 53 of that weekday, which happens whenever the year starts on the payday, and one day earlier in a leap year.

Assuming every year is 365 days in a long calculation. Over a decade the leap days add up to two or three, 48 to 72 hours, which is why interest, depreciation and anything else that runs for years is counted on real dates rather than converted. Use the 365.2425 setting for a fair average, or the date duration calculator for the exact count.

Assuming every day is 24 hours. In local time the day the clocks go forward has 23 hours and the day they go back has 25. Elapsed time across those days should be measured in UTC, or in seconds since the epoch, and converted afterwards.

Worrying about leap seconds. They exist, 27 have been added since 1972 and none since 2016, but civil timekeeping ignores them for every purpose on this page and they are due to be discontinued by 2035. A day is 86,400 seconds for anything you will ever convert here.

Quoting month and year conversions to six decimals. 0.230137 months in a week is a property of one convention, not of the week. Report those results to two decimals and say which year length you used.

Popular time conversions

The questions people ask most. Each opens the converter on that value with its own address, so you can bookmark or share the exact answer.

How many seconds, minutes and hours

How many days, weeks, months and years

Hours to minutes

Minutes to hours

Seconds to minutes and hours

Hours to days

Days to weeks and months

Weeks to months and years

Pregnancy, notice periods, leases and training plans are counted in weeks and quoted in months. The month here is the 30.4167 day average.

Months to years, weeks and days

Years to days, weeks and seconds

Big numbers

How this was checked

The engine was tested in Node before it went near a browser. The exact integers that anchor the chain, 168 hours in a week, 1,440 minutes and 86,400 seconds in a day, 8,760 hours, 525,600 minutes and 31,536,000 seconds in a 365 day year, and 31,557,600 seconds in a Julian year, all come out exactly, and every one of the hundred unit pairs round trips a value out and back to within a billionth. The calendar functions were checked against the years everybody argues about: 1900 is not a leap year, 2000 is, 2100 will not be; the four hundred years from 2000 add up to 146,097 days and exactly 20,871 weeks; and the ISO week count gives 53 for 2015, 2020 and 2026, 52 for 2021 and 2025, and 71 long years in every 400, which is the published figure.

The whole unit breakdown was cross checked by rebuilding each result from its parts, and the hours and minutes display against hand conversions such as 1.75 hours to 1:45 and 140 minutes to 2:20. The live page was then opened at every address linked above and each one was checked for a distinct title, the right headline and clean CSV, image and print output containing only that value, on a desktop and a phone width screen.

Common questions

How many weeks are in a year?

52 weeks and 1 day, or 52.14 weeks. A common year has 365 days and 52 × 7 is 364, so one day is left over; a leap year leaves two, 52.29 weeks. Counted by the ISO standard, where weeks start on Monday and belong to the year that holds their Thursday, a year has either 52 or 53 whole weeks. 2026 is a 53 week year, and so are 2032 and 2037. Averaged over the Gregorian cycle a year is 365.2425 days, 52.1775 weeks.

How many seconds are in a day, a week and a year?

A day is 24 × 60 × 60 = 86,400 seconds and a week is seven of those, 604,800 seconds. A common year of 365 days is 31,536,000 seconds, a leap year 31,622,400, and the 365.25 day Julian year used in astronomy is exactly 31,557,600 seconds. A million seconds is 11 days, 13 hours, 46 minutes and 40 seconds; a billion seconds is about 31.7 years.

How many hours are in a week, a month and a year?

A week is 168 hours. A month runs from 672 hours in a 28 day February to 744 in a 31 day month, and the average month, one twelfth of a 365 day year, is 730 hours. A year is 8,760 hours, 8,784 in a leap year. For a working year, 52 weeks of 40 hours is 2,080 hours, which is the figure most salary conversions use; the US federal payroll figure of 2,087 comes from averaging in leap years.

How do I convert hours to minutes, and decimal hours to hours and minutes?

Multiply hours by 60: 1.5 hours is 90 minutes, 2.25 hours is 135. To turn a decimal into hours and minutes, keep the whole hours and multiply the fraction by 60, so 1.75 hours is 1 hour and 0.75 × 60 = 45 minutes, written 1:45. Going the other way, divide the minutes by 60: 1 hour 20 minutes is 1 + 20 ÷ 60 = 1.33 hours. The common slip is reading 1.5 hours as 1 hour 50 minutes; it is 1 hour 30.

How many minutes are in a day?

1,440. A day has 24 hours of 60 minutes and 24 × 60 = 1,440. A week is 10,080 minutes, a 30 day month is 43,200, and a 365 day year is 525,600 minutes. The converter shows the same value in every unit at once, so 1,440 minutes also appears as 86,400 seconds, 0.1429 weeks and 0.00274 years.

How many days and weeks are in a month?

Between 28 and 31 days, which is why a month is the one unit on this page without a fixed value. The average over a year is 365 ÷ 12 = 30.4167 days, or 4.35 weeks, so 3 months is about 13 weeks, 6 months is 26 weeks and a day, and 12 weeks is only 2.76 months, not 3. Set the month length to 28, 29, 30 or 31 days in the converter if you mean a particular month.

Related Calculators and Reference

• Date Duration Calculator: count the real days, weeks and months between two dates on the calendar, which is the right tool once leap years and month lengths start to matter.
• Timesheet Duration Calculator: hours and minutes between clock times, in decimal hours for payroll, with overtime.
• Hourly to Salary Calculator: the 2,080 hour working year in use, turning a rate into weekly, monthly and annual pay.
• Epoch Converter: seconds since 1 January 1970, the largest number of seconds most people ever convert, into dates in any time zone.
• Age Calculator: years, months and days between a birth date and today, counted on the real calendar rather than averaged.
• Military Time Converter: the 24 hour clock against the 12 hour one, for the times of day that these durations sit between.
• Sleep Calculator: bedtimes and wake times by sleep cycle.
• Time Calculator: add and subtract times in hours, minutes and seconds.
• BIPM, the SI second: the definition of the base unit that every factor on this page is built from.