Time Unit Converter

The exact steps are 60 seconds per minute, 60 minutes per hour, 24 hours per day and 7 days per week. So 1 hour is 3,600 seconds and 1 day is 1,440 minutes. Those ratios never change, because they are definitions, not measurements.

The second itself used to be defined as a fraction of Earth's rotation — 1/86,400 of a mean solar day. That definition was retired because the planet's spin is not perfectly steady. Since 1967 the SI second has instead been defined atomically: 9,192,631,770 oscillations of radiation from a cesium-133 atom. Every clock, phone and server ultimately traces its timekeeping back to that fixed physical constant, not to the sky.

Months and years vary in length, so this converter uses average values: a month is 30.44 days and a year is 365.25 days. That 365.25 is the length of a Julian year — the old Roman calendar's rule of one leap day every 4 years, no exceptions. The Gregorian calendar actually in use refines that slightly, skipping the leap day in century years not divisible by 400 (2000 was a leap year, 1900 and 2100 are not), which makes the true average calendar year 365.2425 days — close to the Julian figure, but not identical. For exact calendar spans between two real dates, use the days-between-dates calculator instead of this average-based one.

A time span written in decimal hours does not read like clock time, and mixing the two up is a classic payroll and timesheet error. 1.5 hours is 1 hour and 30 minutes — not 1 hour and 50 minutes, even though "50" is what an untrained eye reaches for out of ".5 looks like 50." The ".5" is half of 60 minutes, not half of 100. The same trap catches 0.25 h (15 minutes, not "25 minutes") and 0.75 h (45 minutes, not "75"). This converter's minutes output sidesteps the trap entirely — enter hours and read the exact minute figure rather than eyeballing the decimal.

Even the atomic second needs the occasional adjustment against the (slightly irregular) real-world day: a leap second has periodically been inserted to keep atomic clocks and Earth's rotation from drifting apart. In 2022 the General Conference on Weights and Measures (CGPM) — the international body that governs the SI system — voted to discontinue leap seconds by 2035, favoring a large one-time adjustment far in the future over the disruptive, unpredictable insertions of the past. It does not change any of the conversions on this page, but it is why "a day" is a slightly moving target at the level of precision atomic clocks operate at.