There are 1,440 minutes in a day, and 86,400 seconds. Both come straight from the sexagesimal clock: 24 hours to a day, 60 minutes to an hour, 60 seconds to a minute.
The number 1,440 turns up often enough in productivity writing to have become a slogan — the idea being that everyone gets the same 1,440 minutes. As arithmetic it is exact; as advice it skips over the fact that people do not get to choose how much of that budget is already committed.
| Period | Minutes | Seconds | Hours |
|---|---|---|---|
| 1 hour | 60 | 3,600 | 1 |
| ½ day | 720 | 43,200 | 12 |
| 1 day | 1,440 | 86,400 | 24 |
| 1 week | 10,080 | 604,800 | 168 |
| 30 days | 43,200 | 2,592,000 | 720 |
| 1 common year (365 d) | 525,600 | 31,536,000 | 8,760 |
| 1 leap year (366 d) | 527,040 | 31,622,400 | 8,784 |
The 525,600 figure for a common year is the one from the song “Seasons of Love” in the musical Rent — “five hundred twenty-five thousand six hundred minutes” is arithmetically exact for a 365-day year.
Why 24 and 60, and not 10 and 100
The clock is the last widely used remnant of base-60 counting, and it comes from ancient Mesopotamia. The Sumerians and later Babylonians used a sexagesimal system, and 60 is unusually convenient for division: it splits evenly by 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30.
The 24-hour day came separately, from ancient Egypt, where daylight and night were each divided into 12 parts. Because those parts varied in length with the seasons, hours were originally unequal — fixed 60-minute hours only became standard with mechanical clocks.
Decimal time has been tried. Revolutionary France introduced a 10-hour day of 100 minutes each in 1794, giving 1,000 decimal minutes per day. It was abandoned within about 18 months: the arithmetic was tidier, but every clock in the country would have had to be replaced, and 60’s divisibility turned out to be worth more in daily use than base-10 neatness.
The day is not exactly one rotation
The 86,400-second day is a definition, not a measurement, and the Earth does not quite cooperate.
- A solar day — noon to noon — averages 86,400 seconds, but varies through the year by up to about 30 seconds either side because the Earth’s orbit is elliptical and its axis is tilted
- A sidereal day, one rotation relative to the distant stars, is about 23 hours 56 minutes 4 seconds — roughly 1,436.07 minutes. It is shorter because the Earth also moves along its orbit, so it must turn slightly more than 360° to bring the Sun back overhead
- The Earth’s rotation is also gradually slowing, by a couple of milliseconds per century
Civil time handles the mismatch with leap seconds, which have been added 27 times since 1972 to keep atomic clocks aligned with the Earth’s rotation. In 2022 the General Conference on Weights and Measures resolved to abandon the practice by 2035, letting the two drift apart instead — accumulated discrepancy is easier to manage than irregular one-second jumps in software.
Working with 1,440
Some conversions that come up in scheduling and shift planning:
- 1% of a day = 14.4 minutes
- A third of a day = 480 minutes = 8 hours, the standard work shift
- A 12-hour shift = 720 minutes
- 90 minutes = 6.25% of a day, roughly one sleep cycle
- 1,440 minutes ÷ 7 = 205.7 minutes, so a seventh of a day is about 3 hours 26 minutes
For duration arithmetic across midnight — the case that trips up spreadsheets — the reliable method is to convert both clock times to minutes since midnight, subtract, and add 1,440 if the result is negative. An 11:00 pm to 7:00 am shift is (7 × 60) − (23 × 60) = −960, plus 1,440 = 480 minutes, or 8 hours.
Frequently Asked Questions
How many minutes are in a day?
1,440 minutes. A day is 24 hours and each hour is 60 minutes, so 24 × 60 = 1,440.
How many seconds are in a day?
86,400 seconds — 1,440 minutes × 60. The civil day is defined as exactly 86,400 seconds, even though the Earth’s actual rotation varies slightly.
How many minutes are in a week?
10,080 minutes, which is 1,440 × 7. That is also 604,800 seconds, or 168 hours.
How many minutes are in a year?
525,600 minutes in a common year of 365 days, and 527,040 in a leap year. The 525,600 figure is the one in the song “Seasons of Love” from Rent.
Why are there 60 minutes in an hour instead of 100?
Because the clock inherited base-60 counting from ancient Mesopotamia, and 60 divides evenly by 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30. Revolutionary France tried a decimal clock in 1794 and abandoned it within about 18 months.
Is a day exactly 24 hours?
For civil timekeeping, yes — the day is defined as exactly 86,400 seconds. The actual solar day varies by up to about 30 seconds through the year, and a sidereal day is about 23 hours 56 minutes.