Revolutions per minute
- For the Rise Against album, see Revolutions Per Minute (album).
The revolutions per minute (abbreviated rpm, RPM or r/min) is a unit of frequency, commonly used to measure rotational speed. Examples:
- Gramophone (phonograph) records typically rotate at 16, 33⅓, 45, or 78 rpm (CAV).
- Audio CD rotation rates vary from about 500 rpm when reading the innermost CD track, to 180 rpm when reading tracks near the outer edge (CLV).
- An automobile's engine typically makes between 700 and 7000 rpm.
- Piston aircraft engines can rotate with 8000 rpm.
- A racing car engine's limits are much higher, as high as 19,000 rpm in Formula One.
- Gas turbine engines rotate at tens of thousands of rpm.
- A computer's hard drive can range from 3000-7200 RPM on IDE types and from 10,000 to 25,000 on SATA and SCSI drives.
- A 52x CD-ROM drive can rotate a CD as fast as 10,350 RPM.
- Zippe-type centrifuge spins at 90,000 RPM.
Standards bodies generally recommend the symbol r/min, which better follows the general principles for forming unit symbols.
The SI unit of frequency is the hertz (Hz):
- 1 rpm = 1 r/min = 1/60 Hz
The SI unit of angular speed is the radian per second:
- 1 rpm = 1 r/min = 2π rad/min = 2π/60 rad/s = 0.10471976 rad/s