Time Converter (seconds, hours, days, years)
Convert time between milliseconds, seconds, minutes, hours, days, weeks, months, and years — one value into every unit.
Time conversion reference
| 1 unit | s | min | h | d |
|---|---|---|---|---|
| 1 ms | 0.001 | 0.0000166667 | 0.000000277778 | 0.0000000115741 |
| 1 s | 1 | 0.0166667 | 0.000277778 | 0.0000115741 |
| 1 min | 60 | 1 | 0.0166667 | 0.000694444 |
| 1 h | 3 600 | 60 | 1 | 0.0416667 |
| 1 d | 86 400 | 1 440 | 24 | 1 |
| 1 wk | 604 800 | 10 080 | 168 | 7 |
| 1 mo | 2 592 000 | 43 200 | 720 | 30 |
| 1 yr | 31 536 000 | 525 600 | 8 760 | 365 |
Converting time units
Time is the one everyday quantity that isn't decimal: 60 seconds to a minute, 60 minutes to an hour, 24 hours to a day. Those mixed factors make mental conversion awkward, which is what this tool is for — enter a value in any unit and see it in all of them.
The numbers behind it
An hour is 3600 seconds and a day is 86 400. A week is 604 800 seconds. Those three cover most practical conversions: a duration in seconds divided by 3600 gives hours, and divided by 86 400 gives days.
Months and years are approximations
Unlike the smaller units, months and years don't have a fixed length. Months run from 28 to 31 days, and a calendar year is 365 days except in leap years. This converter uses a 30-day month and a365-day year, which is standard for rough duration work but won't match a real calendar. For exact spans between two dates — where leap years and month lengths matter — use thedate difference calculator instead.
Worked example
A 90-minute film is 1.5 hours, or 5400 seconds. A process that takes 500 000 seconds runs for 500 000 / 86 400 ≈ 5.79 days. Timing something much shorter? A millisecond is a thousandth of a second, so a 250 ms response is 0.25 s.
Common questions
- Is 604,800 seconds exactly one week?
- Yes, exactly. A week is 7 days, a day is 86,400 seconds, and 7 × 86,400 = 604,800 with nothing left over. That exactness holds because the second, minute, hour and day are defined in fixed ratios to one another — unlike months and years, which are not.
- Why does a year convert as 365.25 days here?
- Because that is the average length of a year once leap years are counted: three years of 365 days and one of 366 average to 365.25. This is the Julian year, and it is the convention used in astronomy and in most unit conversion. A calendar year is either 365 or 366 days and never 365.25, so if you are counting actual dates rather than converting a duration, use the date difference calculator instead.
- How long is a month in seconds?
- There is no single answer, which is why this converter does not offer months. Real months run from 28 to 31 days — a spread of over 10% — so any single figure would be wrong most of the time. Where a calculation genuinely needs a month, it usually means either 30 days or one twelfth of a year (30.4375 days); decide which you mean and convert that instead.
- Why does my answer differ slightly from another converter?
- Almost always because of the year. Some tools use 365 days, some 365.25, and a few use the tropical year of 365.2422. Over a single year the difference is hours; over a century it is weeks. This converter uses 365.25 days and says so, so you can tell whether a discrepancy is a real error or just a different convention.