Convert milliseconds, seconds, minutes, hours, days, weeks, months, and years precisely.
One duration can be written in eight different units, and this tool shows them all for a single entry: type 3 days, 1,500 milliseconds, or 0.25 hours, and every equivalent - minutes, seconds, weeks, and the rest - appears at once, with the arithmetic done for you. Below the month, every ratio is exact: 60 seconds to a minute, 3,600 to an hour, 86,400 to a day. Months and years are where it gets surprising - their calendar lengths vary, so results in those units follow a fixed average convention rather than any real calendar.
A concrete input and expected output from the current implementation.
Input
1.5 hours
Expected output
90 minutes, 5,400 seconds, 5,400,000 milliseconds, 0.0625 days
Each figure follows by multiplying: 1.5 hours is 1.5 x 60 = 90 minutes, 90 x 60 = 5,400 seconds, and 5,400 x 1,000 = 5,400,000 milliseconds; 1.5 / 24 = 0.0625 days. These ratios are exact, so the whole set is consistent.
The entered value is multiplied by the fixed ratio of its chosen unit - 1,000 milliseconds, 3,600 seconds, or 86,400 seconds per day - into a common base, then divided by each other unit's ratio to produce every equivalent. Because all outputs come from the same base figure, they agree with each other, and a figure in one unit can be cross-checked against any other output on screen.
Calendar months run 28 to 31 days and a year is 365 or 366, so no fixed factor fits every case. The tool applies one average length for months and one for years and converts with those. The figures are internally consistent, but they are not calendar arithmetic: over spans of several months, adding up real dates can shift the total by days.
Because months have 28 to 31 days and years have 365 or 366, no single factor is correct for every case. The tool applies one fixed average length per unit, so its month and year figures are exact only relative to that convention. If your span crosses specific dates, total the days by hand instead; calendar totals can differ by several days.
Not for calendar math. The tool converts a duration into other durations; it does not place a result on a timeline. Adding a duration to a real timestamp has to account for time zones and daylight-saving time, where a day can be 23 or 25 hours. Do that in a date-and-time calculator instead.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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