Revolutions per minute (abbreviated rpm, RPM, r/min, or r·min−1) is a unit of frequency: the number of full rotations completed in one minute around a fixed axis. Frequency is a measure of the number of occurrences of a repeating event per unit Time. Rotational motion can occur around more than one axis at once and can involve phenomena such as wobbling and Precession. It is most commonly used as a measure of rotational speed or angular velocity of some mechanical component. Rotational speed (sometimes called speed of revolution) indicates for example how fast a motor is running Do not confuse with Angular frequency The unit for angular velocity is rad/s

Standards organizations generally recommend the symbol r/min, which is more consistent with the general use of unit symbols. A standards organization, standards body, standards development organization or SDO is any entity whose primary activities are developing coordinating This is not enforced as an international standard; in French, for example, tr/mn (tours par minute) is commonly used.

The corresponding International System of Units (SI) unit would be the hertz and we have:

3600 r/min = 60 revolutions per second = 60 Hz

In the SI one often uses the unit for angular velocity which is radians per second (rad·s−1):

1 r/min = 2π rad·min−1 = 2π/60 rad·s−1 ≈ 0. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. The second ( SI symbol s) sometimes abbreviated sec, is the name of a unit of Time, and is the International System of Units The radian per second (symbol rad·s&minus1 or rad/s) is the SI unit of Angular velocity. 10471976 rad·s−1

To convert revolutions per minute to revolutions per second (hertz), simply divide by 60.

## Examples

• On some kinds of disc or tape-like recording media, the rotational speed of the medium under the read head is a standard given in r/min. This page is a progressive and labeled list of the SI Angular velocity orders of magnitude with certain examples appended to some list objects Gramophone (phonograph) records, for example, typically rotate steadily at 16, 33⅓, 45 or 78 r/min (⁴⁄₁₅, ⁵⁄₉, ³⁄₄, or 1. A gramophone 3 Hz).
• Modern dental drills can rotate at up to 500,000 r/min (8 kHz). A dental drill (or dentist's drill) is a small high-speed Drill used in Dentistry to remove decayed tooth material prior to the insertion of a Dental
• The "second" hand of a conventional analogue clock rotates at 1 r/min.
• Audio CD players read their discs at a constant 150 kB/s and thus must vary the disc's rotational speed from around 500 r/min (actually 8 Hz), when reading at the innermost edge, to 200 r/min (actually 3. 5 Hz) at the outer edge. [1] CD-ROM drives’ maximum rotational speeds are rated in multiples of this figure, even though they do not hold to constant read speeds when reading from most disc formats.
• DVD players also usually read discs at a constant linear rate. DVD (also known as " Digital Versatile Disc " or " Digital Video Disc " - see Etymology)is The disc's rotational speed varies from 1530 r/min (actually 25. 5 Hz), when reading at the innermost edge, and 630 r/min (actually 10. 5 Hz) at the outer edge. [1] DVD drives’ speeds are are usually given in multiples of this figure.
• A washing machine's drum may rotate at 500 to 2000 r/min (8–33 Hz) during the spin cycles. A washing machine, or washer, is a machine designed to clean Laundry, such as Clothing, Towels and sheets The term is mostly applied
• An automobile's engine typically varies between 700 and 7000 r/min (12–120 Hz) though some cars’ engines can spin as quickly as 11,000 r/min (180 Hz). An engine is a mechanical device that produces some form of output from a given input
• A piston aircraft engine typically rotates at a rate between 2000 and 3000 r/min (30–50 Hz). An aircraft engine is a Propulsion system for an Aircraft. Aircraft engines are almost always a type of lightweight Internal combustion engine.
• Computers’ hard drives typically rotate at 5400 or 7200 r/min (90 or 120 Hz)—most commonly with ATA or SATA interfaces—and some high-performance drives rotate at 10,000 or 15,000 r/min (160 or 250 Hz)—usually with SATA, SCSI or Fibre Channel interfaces. A hard disk drive ( HDD) commonly referred to as a hard drive, hard disk, or fixed disk drive, is a Non-volatile storage device AT Attachment with Packet Interface ( ATA/ATAPI) is a standard interface used to connect storage devices such as Hard disks Solid-state Fibre Channel, or FC, is a Gigabit -speed network technology primarily used for Storage networking.
• The engine of a Formula One racing car can reach 19,000 r/min (320 Hz) under some circumstances. A modern Formula One car is a single-seat open cockpit open wheel race car with substantial front and rear wings and engine positioned behind the driver [2]
• A Zippe-type centrifuge for enriching uranium spins at 90,000 r/min (1,500 Hz) or faster. The Zippe-type centrifuge is a device designed to collect Uranium-235. [3]
• Gas turbine engines rotate at tens of thousands of r/min. A gas turbine, also called a combustion turbine, is a rotary Engine that extracts energy from a flow of Combustion gas JetCat model aircraft turbines are capable of over 100,000 r/min (1,700 Hz) with the fastest reaching 165,000 r/min (2,750 Hz). [4]
• An electromechanical battery (EMB) works at 60,000–200,000 r/min (1–3 kHz) range using a passively magnetic levitated flywheel in vacuum. An electromechanical battery (EMB is a device to store Energy in a Flywheel,with some Motor to accelerate it and some Generator to draw energy [5] The choice of the flywheel material is not the most dense, but the one that pulverises the most safely, at surface speeds about 7 times the speed of sound.
• A turbocharger can reach 290,000 r/min (4,800 Hz), while 80,000–200,000 r/min (1–3 kHz) is common. A turbocharger, or turbo, is an air Compressor used for forced-induction of an Internal combustion engine.