Time Converter
Convert between seconds, minutes, hours, days, weeks, months and years.
Written by Rahman · Last reviewed
Quick answer
Time conversion runs through the second. One hour is 3,600 seconds, one day is 86,400 and one week is 604,800. Longer units are necessarily approximate: this converter uses 30.44 days for a month and 365.25 days for a year, which averages leap years correctly but will not match any particular calendar month.
| Second (s) | 1 |
| Millisecond (ms) | 1000 |
| Microsecond (µs) | 1000000 |
| Nanosecond (ns) | 1000000000 |
| Minute (min) | 0.01666666667 |
| Hour (h) | 0.0002777777778 |
| Day (d) | 0.00001157407407 |
| Week (wk) | 0.000001653439153 |
| Month (30.44 days) (mo) | 3.802649e-7 |
| Year (365.25 days) (yr) | 3.168809e-8 |
| Decade (dec) | 3.168809e-9 |
| Century (c) | 3.168809e-10 |
About the Time Converter
Time converters move values between seconds, minutes, hours, days, weeks, months, years and beyond. The second is the SI base unit, and all other units are defined as multiples of it.
This tool is handy for scheduling, project planning and any calculation that mixes different time units.
Months and years have no fixed length, so this converter picks one
Seconds, minutes, hours, days and weeks convert exactly because each is a fixed multiple of the last. Months and years are not, so any converter handling them has to choose a definition, and the choice should be visible rather than hidden.
This one uses 30.44 days for a month and 365.25 days for a year. The year figure is the Julian year, which assumes a leap year every four years; the month is a separate average (the Gregorian mean year, 365.2425 days, divided by twelve) rather than derived from the year figure above it, so converting exactly 1 year gives about 12.0002 months, not a clean 12. Either way it is an average month rather than any real one. A 31-day month is about 1.9% longer than the figure used here.
- For durations spanning specific calendar dates, count the actual days instead. The date difference calculator does this without averaging.
- Contracts and interest calculations often specify their own convention, such as 30-day months or a 360-day year, and those override any general-purpose figure.
- Averaged months are appropriate for rates and long-run estimates, not for deadlines.
Where the calendar stops being arithmetic
The Gregorian leap rule is nearly but not exactly four-yearly: century years are skipped unless divisible by 400, so 1900 was not a leap year and 2000 was. That is why the true average year is slightly under 365.25 days and why the Julian figure used here drifts over very long spans.
Two further irregularities affect real elapsed time. Daylight saving transitions produce days of 23 and 25 hours in the regions that observe them, and leap seconds have occasionally been inserted to keep clocks aligned with the Earth's rotation, so a day is not always exactly 86,400 seconds of elapsed time.
- For scheduling across regions, work in local times rather than in converted durations. The timezone converter handles the transitions.
- Astronomical and financial systems each use their own year definitions, so a figure taken from one domain will not match another.
- Elapsed-time calculations in software normally use a monotonic clock precisely to avoid these irregularities.
Frequently Asked Questions
How many seconds are in a day?
⌄
There are 86,400 seconds in a day (24 hours × 60 minutes × 60 seconds).
How many hours are in a year?
⌄
A standard 365-day year has 8,760 hours; a 365.25-day year averages about 8,766 hours.
How long is a month in this converter?
⌄
For conversions, a month is treated as an average of about 30.44 days, since calendar months vary from 28 to 31 days.