Second (s) Conversions
Use this second converter to convert seconds into milliseconds, microseconds, nanoseconds, minutes, hours, days, weeks, and other supported time units.
1 s = 1,000 ms = 1,000,000 µs = 1,000,000,000 ns
Definition of the Second
The second, with the symbol s, is the SI base unit of time. It provides the reference from which minutes, hours, days, and smaller metric time units are defined.
In the International System of Units, the second is defined by fixing the frequency of a specific transition in the cesium-133 atom at exactly 9,192,631,770 hertz.
In practical terms, one second corresponds to the duration of 9,192,631,770 periods of radiation associated with this cesium-133 transition under the conditions specified by the SI definition.
This atomic definition allows laboratories around the world to reproduce the second with exceptional consistency instead of relying on the slightly irregular rotation of Earth.
Second Conversion Links to Other Time Units
Convert Second (s) to any other supported time unit:
Why Is the Second Important?
The second is one of the seven SI base units. It is fundamental not only to time measurement but also to units that contain time, including meters per second, hertz, watts, volts, and amperes.
Accurate seconds are essential for navigation, telecommunications, computing, scientific experiments, electrical systems, financial networks, satellite positioning, and international timekeeping.
Because the second is the base time unit, this converter expresses every supported time unit as an equivalent number of seconds before calculating the target value.
History of the Second
The idea of dividing time into smaller parts developed from ancient base-60 mathematics. Sumerian and Babylonian mathematicians used a sexagesimal number system, and later astronomers applied divisions by 60 to circles and astronomical observations.
The astronomer Claudius Ptolemy described dividing a degree into 60 first parts and then dividing each of those into 60 second parts. These astronomical subdivisions later influenced the division of hours into minutes and seconds.
The word second is related to the Latin expression pars minuta secunda, meaning the “second small part.” It referred to the second division by 60: an hour was first divided into minutes, and each minute was then divided into seconds.
Early clocks could not measure seconds reliably. As mechanical clocks improved, second hands became practical, allowing shorter intervals to be observed directly.
From the Solar Second to the Atomic Second
The second was historically connected to Earth's rotation. A mean solar day was divided into 24 hours, each hour into 60 minutes, and each minute into 60 seconds, giving 24 × 60 × 60 = 86,400 seconds per day.
Earth's rotation is not perfectly uniform, so it could not support increasingly precise scientific measurements. During the twentieth century, the definition was changed from an astronomical fraction of the day to a value based on Earth's orbit and then to an atomic standard.
In 1967, the international measurement community adopted a definition based on the cesium-133 atom. The modern SI continues to define the second using the fixed cesium frequency of exactly 9,192,631,770 hertz.
Second Conversion Basics
The second is the common reference unit for time conversions, so its base factor is 1.
Target value = Seconds ÷ Target-unit seconds factor
For example, one minute has a factor of 60 seconds. Converting 180 seconds to minutes gives 180 ÷ 60 = 3 minutes.
To convert another time unit into seconds, multiply the original value by its seconds factor. For example, 2 hours × 3,600 = 7,200 seconds.
Common Second Conversion Formulas
- Milliseconds = Seconds × 1,000
- Microseconds = Seconds × 1,000,000
- Nanoseconds = Seconds × 1,000,000,000
- Minutes = Seconds ÷ 60
- Hours = Seconds ÷ 3,600
- Days = Seconds ÷ 86,400
- Weeks = Seconds ÷ 604,800
Common Second Conversions
| Target unit | Equivalent to 1 second |
|---|---|
| Nanoseconds | 1,000,000,000 ns |
| Microseconds | 1,000,000 µs |
| Milliseconds | 1,000 ms |
| Minutes | 1/60 min ≈ 0.0166667 min |
| Hours | 1/3,600 h ≈ 0.000277778 h |
| Days | 1/86,400 d ≈ 0.0000115741 d |
| Weeks | 1/604,800 week ≈ 0.00000165344 week |
| Average months | Approximately 0.000000380517 month |
| Average Gregorian years | Approximately 0.0000000316887 year |
Conversions to metric submultiples, minutes, hours, standard days, and weeks use fixed factors. Month and year results depend on the average or calendar definition selected by the converter.
Metric Subdivisions of a Second
SI prefixes create smaller units by dividing the second by powers of ten. A millisecond is one-thousandth of a second, a microsecond is one-millionth, and a nanosecond is one-billionth.
- 1 ms = 10−3 s
- 1 µs = 10−6 s
- 1 ns = 10−9 s
- 1 ps = 10−12 s
- 1 fs = 10−15 s
These small units are useful in electronics, computer processing, telecommunications, physics, chemistry, and precision measurement.
Elapsed Seconds and Clock Time
Elapsed seconds measure a duration, while clock time identifies a position within a day. For example, 3,600 elapsed seconds represents one hour of duration, but it does not identify a particular hour on a clock.
When calculating elapsed seconds between dates or local clock times, time zones, daylight-saving transitions, and calendar changes may need to be considered before performing the unit conversion.
Second Conversion FAQ
Why is the second an SI base unit rather than the minute?
The second was selected as the base time unit because it provides a practical scale for scientific measurement and can be reproduced precisely using an atomic frequency. Minutes and hours are defined as fixed multiples of the second.
Why is the modern second based on a cesium atom?
Cesium-133 atoms provide a stable and reproducible natural frequency. Unlike Earth's rotation, this atomic frequency does not vary with weather, tides, or changes in the planet's motion.
Is the atomic second different from an everyday second?
No. Atomic clocks provide the precise realization of the same second used by clocks, computers, laboratories, navigation systems, and everyday timekeeping.
Why does converting one second to minutes produce a repeating decimal?
One second is exactly 1/60 of a minute. Because 1/60 does not have a terminating decimal representation, it becomes 0.0166666… minutes.
Is 0.0166667 minute an exact representation of one second?
No. It is a rounded approximation. The exact value is 1/60 minute.
Why are milliseconds, microseconds, and nanoseconds based on 1,000?
These units use SI decimal prefixes. Each step from seconds to milliseconds, microseconds, or nanoseconds changes the scale by a power of 1,000.
What is the difference between frequency and time?
Time measures duration, while frequency measures the number of repeating events per second. Frequency is measured in hertz, where 1 Hz = 1 cycle per second.
What is a leap second?
A leap second is an occasional adjustment historically applied to Coordinated Universal Time to keep civil time close to Earth's irregular rotation. It does not change the SI definition of the second.
Does converting seconds improve measurement accuracy?
No. Conversion changes only the unit and numerical representation. A duration measured to the nearest second does not become accurate to the nearest millisecond simply because it is multiplied by 1,000.
How can a second conversion be checked?
Perform the inverse calculation and confirm that it returns the original value. For example, 7,200 seconds equals 2 hours, and 2 × 3,600 = 7,200 seconds.
Second Standards and References
Further information about the definition and history of the second is available from international measurement authorities: