Calculators & everyday math
Seconds, Minutes, Hours, Days, and Weeks Explained
Seconds, minutes, hours, days, and weeks are linked by a short chain of fixed numbers: 60, 60, 24, and 7. Because every link is exact, any of these units converts to any other with multiplication or division alone. This guide lays out the chain, where its odd-looking numbers come from, and a few shortcuts worth remembering.
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The chain of fixed ratios
To move down the chain to a smaller unit, multiply by each link you pass; to move up to a larger one, divide. Hours to seconds passes two links of 60, so multiply by 3,600.
- 1 minute = 60 seconds
- 1 hour = 60 minutes = 3,600 seconds
- 1 day = 24 hours = 1,440 minutes = 86,400 seconds
- 1 week = 7 days = 168 hours = 10,080 minutes = 604,800 seconds
Every unit in seconds
| Unit | Seconds |
|---|---|
| 1 millisecond | 0.001 |
| 1 second | 1 |
| 1 minute | 60 |
| 1 hour | 3,600 |
| 1 day | 86,400 |
| 1 week | 604,800 |
Measuring every unit in seconds is exactly how the Time Unit Converter works: one multiplication and one division.
Where 60, 24, and 7 come from
Sixty comes from ancient Babylonian astronomy, which counted in base 60. Sixty divides evenly by 2, 3, 4, 5, 6, 10, 12, 15, 20, and 30, which made fractions of an hour easy to work with long before decimals.
Twenty-four hours goes back to ancient Egypt, which split daytime and nighttime into 12 parts each. The seven-day week follows the Babylonian and Jewish calendars and spread through Roman and later religious use.
How long a second is
Since 1967 the second has been defined by atomic physics: 9,192,631,770 cycles of the radiation from a cesium-133 atom. Minutes, hours, days, and weeks in a unit converter are simply multiples of that second.
The Earth’s actual rotation varies slightly, which is why leap seconds have occasionally been added to clock time. A fixed-unit converter uses the standard 86,400-second day and ignores them.
Shortcuts worth remembering
- Minutes to hours: divide by 60 — 150 minutes is 2.5 hours.
- Hours to days: divide by 24 — 36 hours is 1.5 days.
- Days to hours: multiply by 24 — a week is 168 hours.
- A quarter hour is 15 minutes, and a tenth of an hour is 6 minutes.
Seconds to Weeks Explained FAQ
- How many hours are in a week?
- 168: 7 days × 24 hours.
- How many minutes are in a day?
- 1,440: 24 hours × 60 minutes.
- How many seconds are in a week?
- 604,800: 7 × 24 × 60 × 60.
- Why isn’t time decimal, like meters?
- Base 60 and 24-hour days long predate the metric system. Decimal time was tried in France in the 1790s but was abandoned after a few years.
- Is a day always exactly 86,400 seconds?
- A standard day is. Clock time occasionally gains a leap second, and a local calendar day can be 23 or 25 hours when clocks change for daylight saving time.
Related guides
- Milliseconds to SecondsWhere milliseconds appear in code, timers, and media, how to convert them to seconds and minutes, and a table of common millisecond values.
- Days in a YearCommon and leap years, the Gregorian leap-year rule, average year lengths used in science, and why a year can’t be a fixed time unit.
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