A microsecond is an SI unit of time equal to one millionth (0.000001 or 10−6 or 11,000,000) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available.

A microsecond is equal to 1000 nanoseconds or 11,000 of a millisecond. Because the next SI prefix is 1000 times larger, measurements of 10−5 and 10−4 seconds are typically expressed as tens or hundreds of microseconds.


  • 1 microsecond (1 μs) – cycle time for frequency 1×106 hertz (1 MHz), the inverse unit. This corresponds to radio wavelength 300 m (AM medium wave band), as can be calculated by multiplying 1 μs by the speed of light (approximately 3.00×108 m/s) to determine the distance travelled.
  • 1 microsecond – the length of time of a high-speed, commercial strobe light flash (see air-gap flash).
  • 1.8 microseconds – the amount of time subtracted from the Earth's day as a result of the 2011 Japanese earthquake.[1]
  • 2 microseconds – the lifetime of a muonium particle
  • 2.68 microseconds – the amount of time subtracted from the Earth's day as a result of the 2004 Indian Ocean earthquake.[2]
  • 3.33564095 microseconds – the time taken by light to travel one kilometer in a vacuum
  • 5.4 microseconds – the time taken by light to travel one mile in a vacuum (or radio waves point-to-point in a near vacuum)
  • 8.01 microseconds – the time taken by light to travel one mile in typical single-mode fiber optic cable
  • 10 microseconds (μs) – cycle time for frequency 100 kHz, radio wavelength 3 km
  • 18 microseconds – net amount per year that the length of the day lengthens, largely due to tidal acceleration.[3]
  • 20.8 microseconds – sampling interval for digital audio with 48,000 samples/s
  • 22.7 microseconds – sampling interval for CD audio (44,100 samples/s)
  • 38 microseconds – discrepancy in GPS satellite time per day (compensated by clock speed) due to relativity[4]
  • 50 microseconds – cycle time for highest human-audible tone (20 kHz)
  • 50 microseconds to read – the access latency for a modern solid state drive which holds non-volatile computer data[5]
  • 100 microseconds (0.1 ms) – cycle time for frequency 10 kHz
  • 125 microseconds – sampling interval for telephone audio (8000 samples/s)
  • 164 microseconds – half-life of polonium-214
  • 240 microseconds – half-life of copernicium-277
  • 250 microseconds – cycle time for highest tone in telephone audio (4 kHz)
  • 277.8 microseconds – a fourth (a 60th of a 60th of a second), used in astronomical calculations by al-Biruni and Roger Bacon in 1000 and 1267 AD, respectively.[6][7]
  • 489.67 microseconds – time for light at a 1550 nm frequency to travel 100 km in a singlemode fiber optic cable (where speed of light is approximately 200 million meters per second due to its index of refraction).
  • The average human eye blink takes 350,000 microseconds (just over 1/3 of one second).
  • The average human finger snap takes 150,000 microseconds (just over 1/7 of one second).
  • A camera flash illuminates for 1000 microseconds.
  • Standard camera shutter speed opens the shutter for 4000 microseconds or 4 milliseconds.

See also


  1. Gross, R.S. (14 March 2014). "Japan quake may have shortened Earth days, moved axis". JPL News. Jet Propulsion Laboratory. Retrieved 23 August 2019.
  2. Buis, Alan (January 10, 2005). "NASA Details Earthquake Effects on the Earth". NASA. Retrieved June 29, 2011.
  3. MacDonald, Fiona. "Earth's Days Are Getting 2 Milliseconds Longer Every 100 Years". ScienceAlert. Retrieved 2017-03-08.
  4. Richard Pogge. "GPS and Relativity". Retrieved 2011-10-01.
  5. Intel Solid State Drive Product Specification
  6. al-Biruni (1879). The chronology of ancient nations: an English version of the Arabic text of the Athâr-ul-Bâkiya of Albîrûnî, or "Vestiges of the Past". Translated by Sachau C Edward. W.H. Allen. pp. 147–149. OCLC 9986841.
  7. R Bacon (2000) [1928]. The Opus Majus of Roger Bacon. translator: BR Belle. University of Pennsylvania Press. table facing page 231. ISBN 978-1-85506-856-8.
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