90 minutes in hours
- Value
- 90 min
- From
- minute (min)
- To
- hour (h)
- Converted value
- 1.5 h
Checked against: 90 / 60 = 1.5
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.
By AdminDrafted with AI writing toolsUpdated Checked examples: 4
Converted value
h
Converted value: 1.5 h
- 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
90 min in every Time unit
| Unit | Value | Definition |
|---|---|---|
| nanosecond (ns) | 5,400,000,000,000 | 1 ns = 1 × 10⁻⁹ s, exact |
| microsecond (µs) | 5,400,000,000 | 1 µs = 0.000001 s, exact |
| millisecond (ms) | 5,400,000 | 1 ms = 0.001 s, exact |
| second (s) | 5,400 | Base unit |
| minute (min) | 90 | 1 min = 60 s, exact |
| hour (h) | 1.5 | 1 h = 3,600 s, exact |
| day (d) | 0.0625 | 1 d = 86,400 s, exact |
| week (wk) | 0.008928571 | 1 wk = 604,800 s, exact |
| fortnight | 0.004464286 | 1 fortnight = 1,209,600 s, exact |
| month (mo) | 0.00205343 | 1 mo = 2,629,746 s, exact (Average Gregorian month (30.436875 days)) |
| year (yr) | 0.0001711192 | 1 yr = 31,556,952 s, exact (Average Gregorian year (365.2425 days)) |
| decade | 0.00001711192 | 1 decade = 315,569,520 s, exact |
| century | 0.000001711192 | 1 century = 3,155,695,200 s, exact |
| millennium | 1.711192 × 10⁻⁷ | 1 millennium = 31,556,952,000 s, exact |
How it's calculated S
Convert minute to second
1 min = 60 s, exact
Convert second to hour
1 h = 3,600 s, exact
Combined factor
Both units are defined exactly and the converted mathematical value has a terminating decimal. A displayed result may still be rounded.
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.
How to convert time units
Multiply by the number of seconds in the starting unit, then divide by the number in the target unit. The second is the SI base unit; the minute, hour and day are accepted for use alongside it (BIPM, SI Brochure). For 90 minutes: 90 × 60 = 5,400 s, and 5,400 ÷ 3,600 = 1.5 hours. The everyday shortcuts follow from this: divide minutes by 60 for hours, and multiply days by 24 for hours.
Worked conversions
- Hours to minutes: 2.5 h × 60 = 150 min.
- Minutes to seconds: 45 min × 60 = 2,700 s.
- Days to hours: 3 days × 24 = 72 h.
- Weeks to days: 6 weeks × 7 = 42 days.
- A fraction of an hour: one third of 60 minutes is 20 min.
Time units in seconds
Each row gives one unit in seconds. Months and longer units use Gregorian averages, explained below the chart.
| Source unit | Seconds | Convention |
|---|---|---|
| 1 ns | 0.000000001 | Defined factor |
| 1 us | 0.000001 | Defined factor |
| 1 ms | 0.001 | Defined factor |
| 1 s | 1 | Defined factor |
| 1 min | 60 | Defined factor |
| 1 h | 3600 | Defined factor |
| 1 d | 86400 | Defined factor |
| 1 wk | 604800 | Defined factor |
| 1 fortnight | 1209600 | Defined factor |
| 1 mo | 2629746 | Mean Gregorian interval |
| 1 yr | 31556952 | Mean Gregorian interval |
| 1 decade | 315569520 | Mean Gregorian interval |
| 1 century | 3155695200 | Mean Gregorian interval |
| 1 millennium | 31556952000 | Mean Gregorian interval |
A day counts as exactly 86,400 seconds, a week as 7 days and a fortnight as 14. Nano, micro and milli mean one billionth, one millionth and one thousandth of a second.
Decimal hours and hours with minutes
To read decimal hours as a clock duration, multiply only the decimal part by 60. 1.5 h is 1 h 30 min, and 2.4 h is 2 h 24 min.
To go the other way, divide the minutes by 60. 100 minutes is 1.66666666667 h, or 1 h 40 min. Writing it as 1.40 h would record 84 minutes, 16 minutes short.
What a month or year means here
Months and years have no fixed length on the calendar, so they convert as averages. The Gregorian calendar repeats every 400 years with 146,097 days, which gives 365.2425 days per average year and 30.436875 days per average month.
An average rarely matches the months you have in mind. Three average months are 91.310625 days, while January to March of a non-leap year is 90 days. A decade, century and millennium are 10, 100 and 1,000 average years.
Common mistakes
- Writing decimal hours as clock time. 1.5 h is 1:30, not 1:50.
- Using an average month for a due date. For dates, count real calendar days with the date difference calculator or add or subtract days.
- Assuming every local day lasts 24 hours. A day with a daylight-saving change usually lasts 23 or 25 hours on the clock. The hours calculator counts shift hours across such a change.
- Chaining rounded results. 1 s = 0.0166666666667 min is a rounded display. Convert from the original value each time.
Related tools
To add durations written as hours and minutes, such as 1:20 plus 0:45, use the time duration calculator. To change a clock time from one zone to another, use the time zone converter.
Worked examples
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.
About this calculator
Sources
- 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)
- IERS Bulletin C 72 (6 July 2026) — leap-second announcement
- BIPM — Resolution 4 of the 27th CGPM (2022), on the use and future development of UTC
Checked against references
This calculator includes 4 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.