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Time converter

Convert minutes to hours, hours to days, weeks to days and years to seconds, from nanoseconds to millennia, with the 365.2425-day Gregorian year.

Updated Checked against 4 worked examples

A number in the “from” unit, or with its own unit
Try
Converted value
h
Converted value: 1.5 h
Shown to 12 significant figures, half-up
Conversion
90 min = 1.5 h
Conversion factor
0.0166666666667
Exactness
Exact

90 min is exactly 1.5 h. One minute is about 0.01666667 h.

The same amount counted in each unit

min90 minh1.5 h
90 min in every time unit (14 rows)
UnitValueDefinition
nanosecond (ns)5,400,000,000,0001 ns = 1 × 10⁻⁹ s, exact
microsecond (µs)5,400,000,0001 µs = 0.000001 s, exact
millisecond (ms)5,400,0001 ms = 0.001 s, exact
second (s)5,400Base unit
minute (min)901 min = 60 s, exact
hour (h)1.51 h = 3,600 s, exact
day (d)0.06251 d = 86,400 s, exact
week (wk)0.0089285711 wk = 604,800 s, exact
fortnight0.0044642861 fortnight = 1,209,600 s, exact
month (mo)0.002053431 mo = 2,629,746 s, exact (Average Gregorian month (30.436875 days))
year (yr)0.00017111921 yr = 31,556,952 s, exact (Average Gregorian year (365.2425 days))
decade0.000017111921 decade = 315,569,520 s, exact
century0.0000017111921 century = 3,155,695,200 s, exact
millennium1.711192 × 10⁻⁷1 millennium = 31,556,952,000 s, exact
How it's calculated S

  1. Convert minute to second

    90 min×60 smin=5,400 s90\ \text{min} \times 60\ \tfrac{\text{s}}{\text{min}} = 5{,}400\ \text{s}

    1 min = 60 s, exact

  2. Convert second to hour

    5,400 s÷3,600 sh=1.5 h5{,}400\ \text{s} \div 3{,}600\ \tfrac{\text{s}}{\text{h}} = 1.5\ \text{h}

    1 h = 3,600 s, exact

  3. Combined factor

    1 min=603,600 h≈0.0166666666667 h1\ \text{min} = \frac{60}{3{,}600}\ \text{h} \approx 0.0166666666667\ \text{h}

    Both units are defined exactly and the converted value is a terminating decimal, so every digit shown in it is exact.

About the time converter

Every time unit is a fixed number of seconds, the SI second being defined by the caesium-133 frequency of 9,192,631,770 Hz. Minutes, hours, days and weeks are exact multiples; a day is 86,400 s. Months and years vary on the calendar, so the converter uses their Gregorian averages: 365.2425 days a year, from 146,097 days per 400 years, and 30.436875 days a month.

The default converts 90 minutes to 1.5 hours. Timesheets are a common use, where decimal hours become minutes: 7.75 h is 7 h 45 min.

Results ignore leap seconds and daylight-saving changes. For the length of a particular month or year, count its calendar days (28 to 31, or 365 or 366) instead of using the average.

Worked examples

90 minutes in hours

Value
90 min
From
minute (min)
To
hour (h)
Converted value
1.5 h

Checked against: 90 / 60 = 1.5

Average Gregorian year in days

Value
1 yr
From
year (yr)
To
day (d)
Converted value
365.2425 d

Checked against: 146,097 days / 400 years = 365.2425

1 week in seconds

Value
1 wk
From
week (wk)
To
second (s)
Converted value
604,800 s

Checked against: 7 × 24 × 3600 = 604,800

Average month in days

Value
1 mo
From
month (mo)
To
day (d)
Converted value
30.436875 d

Checked against: 365.2425 / 12 = 30.436875

Questions

How many seconds are in a year?

31,556,952 s in an average Gregorian year of 365.2425 days, the year this converter uses. A 365-day year has 31,536,000 s and a 366-day leap year 31,622,400 s. Astronomy uses the Julian year of 365.25 days, 31,557,600 s, which is also the year inside the light-year.

How many days are in a month on average?

30.436875 days. The Gregorian calendar repeats every 400 years with 146,097 days, so a year averages 365.2425 days and a month one twelfth of that. Real months have 28 to 31 days, so use the average for rates and long spans and a calendar for specific dates.

How do I convert decimal hours to hours and minutes?

Multiply the decimal part by 60: 1.5 h is 1 h 30 min, 7.75 h is 7 h 45 min and 0.1 h is 6 minutes. Going the other way, divide minutes by 60, so 90 min is 1.5 h. A timesheet that records 7 h 45 min as 7.45 understates it by 0.3 h.

How many weeks are in a year?

52.1775 weeks in an average Gregorian year (365.2425 ÷ 7). A 365-day year is 52 weeks and 1 day, and a leap year 52 weeks and 2 days. Those spare days add up, which is why a weekly payroll has 53 paydays in some years instead of 52.

Does the converter count leap seconds?

No. Every day here is exactly 86,400 SI seconds. UTC has added 27 leap seconds since 1972, the last on 31 December 2016. In 2022 the General Conference on Weights and Measures (Resolution 4) decided to widen the allowed gap between UTC and Earth-rotation time by 2035, so UTC can run without leap seconds for at least a century.

How accurate is the time converter?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 4 worked examples whose answers come from independent sources; for example, “90 minutes in hours” is checked against 90 / 60 = 1.5.

Where does the method come from?

NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors; NIST Handbook 44, Appendix C — General tables of units of measurement; Gregorian calendar: 146,097 days per 400 years (mean year 365.2425 days).

About this calculator

xto=xfrom×ffromftof=one unit expressed in s\begin{gathered} x_{\text{to}} = x_{\text{from}} \times \dfrac{f_{\text{from}}}{f_{\text{to}}} \\ f = \text{one unit expressed in } \text{s} \end{gathered}

Sources

  1. NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors
  2. NIST Handbook 44, Appendix C — General tables of units of measurement
  3. Gregorian calendar: 146,097 days per 400 years (mean year 365.2425 days)

Checked against references

4 worked examples with independently sourced answers ship with this calculator. They run in the test suite; you can run them here too.

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