Time Unit Converter

How it works

Every unit here is a fixed number of seconds. The calculator multiplies your value by the size of the unit it is in to get seconds, then divides by the size of the unit you want. Milliseconds through weeks are exact: 60 s in a minute, 60 min in an hour, 24 h in a day and 7 days in a week.

Months and years have no single length, so this converter uses the mean Gregorian values. The Gregorian calendar repeats every 400 years, and those 400 years contain exactly 146,097 days (97 of them are leap years). That makes the average year 365.2425 days = 31,556,952 s, and the average month one twelfth of that, 30.436875 days = 2,629,746 s. These are averages: a real calendar month is 28 to 31 days and a real year 365 or 366.

The conversion factor is what one unit of the 'from' unit is worth in the 'to' unit. The table lists the same duration in every unit the converter knows. To find the exact number of days between two dates, use the date difference calculator instead.

Formula

seconds   = value × (size of the from unit in s)
converted = seconds ÷ (size of the to unit in s)
factor    = size of from unit ÷ size of to unit

1 ms = 0.001   1 min = 60   1 h = 3,600   1 day = 86,400   1 week = 604,800
1 month = 2,629,746 (mean Gregorian: 146,097 days ÷ 4,800)
1 year  = 31,556,952 (mean Gregorian: 146,097 days ÷ 400 = 365.2425 days)

Example

1 day, the default, is 86,400 s, which is 86,400 ÷ 3,600 = 24 hours. The factor from days to hours is 24.

The table shows the same day as 86,400,000 ms, 1,440 min, 0.142857 weeks, 0.032855 months and 0.002738 years. Going the other way, 90 minutes is 1.5 hours, one mean year is 365.2425 days or 52.1775 weeks, and one mean month is 30.436875 days.

Assumptions and limitations

• Month and year are mean Gregorian calendar values: 1 year = 365.2425 days = 31,556,952 s and 1 month = 1/12 year = 30.436875 days = 2,629,746 s. A specific calendar month or year is longer or shorter than the average.
• This is not the Julian year of 365.25 days (31,557,600 s) used in astronomy, nor the 365-day common year. The differences are 0.002% and 0.07% respectively.
• All days are exactly 86,400 s. Leap seconds and daylight-saving changes, which make some civil days a second or an hour longer or shorter, are ignored.
• A negative duration is rejected.
• Results are shown to six decimal places; very small values (for example a few milliseconds in years) may display as 0 even though the conversion is computed in full precision.

Frequently asked questions