The microsecond is a unit of time equal to one millionth of a second, or one thousandth of a millisecond. Its symbol is µs, written with the Greek letter mu, and the form us appears where that character is inconvenient to type.
It sits below the threshold of human experience entirely. Nothing a person does or perceives happens on this scale, so the unit belongs wholly to instruments. Light travels about three hundred metres in a microsecond, roughly the length of three football pitches, which sets a hard floor on how fast any signal can cross a room, a circuit board or a continent.
Satellite navigation depends on measuring it accurately. A receiver works out its position from the arrival times of signals from several satellites, and an error of one microsecond in that timing translates into a position error of about three hundred metres. This is why the satellites carry atomic clocks and why the system corrects for relativistic effects: the clocks in orbit run measurably faster than clocks on the ground, by about thirty-eight microseconds a day, and without that correction navigation would drift by kilometres within hours.
Electronics works comfortably at this scale. The switching time of a power transistor, the pulse width in radar, the interval between samples in high-speed data acquisition and the response of an analogue-to-digital converter are all quoted in microseconds. A microcontroller running at one megahertz completes one instruction cycle per microsecond, which makes the unit the natural currency of embedded timing.
Physics and chemistry use it for processes that are fast but not extreme. Muons produced in the upper atmosphere have a mean lifetime of about 2.2 microseconds, and the fact that they reach the ground at all is a direct experimental demonstration of time dilation. Some fluorescence decays, gas-phase reactions and shock-wave phenomena also occupy this range.
Audio engineering encounters it in digital sampling. At the standard rate of 44,100 samples per second, one sample lasts about 22.7 microseconds, and the timing jitter that degrades converter performance is measured in fractions of that.
One microsecond equals 0.000001 seconds, 0.001 milliseconds, or 1000 nanoseconds.
| Unit | Symbol | 1 Microsecond equals | 1 of these equals | Converter |
|---|---|---|---|---|
| Millisecond | ms | 0.001 ms | 1000 µs | Microseconds to Milliseconds |
| Centisecond | cs | 0.0001 cs | 10000 µs | Microseconds to Centiseconds |
| Decisecond | ds | 0.00001 ds | 100000 µs | Microseconds to Deciseconds |
| Second | s | 0.000001 s | 1000000 µs | Microseconds to Seconds |
| Minute | min | 0.0000000166666666667 min | 60000000 µs | Microseconds to Minutes |
| Hour | hr | 2.77777777778 × 10-10 hr | 3600000000 µs | Microseconds to Hours |
| Day | d | 1.15740740741 × 10-11 d | 86400000000 µs | Microseconds to Days |