RPM to Hertz Converter
Our free signal & frequency converter handles rpmto hertz conversions. See tables, ratios, and examples for quick reference.
RPM to Hertz Converter
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Formula: Hertz = RPM / 60 | RPM = Hertz * 60
Worked example โ 2,400 RPM = 40 Hz | 251.33 rad/s
Formula
Hertz = RPM / 60 | RPM = Hertz * 60
Divide RPM by 60 to get hertz since there are 60 seconds per minute. Angular velocity = 2*pi*Hz in rad/s. Linear speed = circumference * frequency for rotating wheels or shafts.
Worked Examples
Example 1: Car Engine at Highway Speed
Problem:A car engine runs at 2,400 RPM. Convert to hertz and find wheel speed with 650mm tires.
Solution:Frequency = 2400 / 60 = 40 Hz Angular velocity = 2 * pi * 40 = 251.33 rad/s Wheel circumference = pi * 0.65 = 2.042 m Linear speed = 2.042 * 40 = 81.68 m/s (with direct drive)
Result:2,400 RPM = 40 Hz | 251.33 rad/s
Example 2: Industrial Motor Speed
Problem:Convert a 1,750 RPM industrial motor speed to hertz.
Solution:Frequency = RPM / 60 f = 1750 / 60 = 29.1667 Hz Period = 1 / 29.1667 = 0.03429 seconds Angular velocity = 2 * pi * 29.1667 = 183.26 rad/s
Result:1,750 RPM = 29.17 Hz (period = 34.29 ms)
Frequently Asked Questions
How do you convert RPM to hertz?
To convert RPM to hertz, divide the RPM value by 60. RPM stands for revolutions per minute, while hertz measures cycles (revolutions) per second. Since there are 60 seconds in a minute, dividing by 60 converts from per-minute to per-second. For example, 3,600 RPM divided by 60 equals 60 Hz, which is the standard US power line frequency.
How can RPM be used to calculate linear speed?
Linear speed from RPM depends on the radius of the rotating object. The formula is v = 2 * pi * r * (RPM/60), where r is the radius in meters and v is speed in meters per second. Alternatively, multiply the circumference (pi * diameter) by the frequency in Hz. A 0.5 meter diameter wheel spinning at 600 RPM moves at pi * 0.5 * 10 = 15.71 m/s or about 56.5 km/h.
What is angular velocity and how does it differ from RPM?
Angular velocity measures rotational speed in radians per second, while RPM measures revolutions per minute. One revolution equals 2*pi radians, so angular velocity = 2*pi * RPM/60. Angular velocity is the standard unit in physics equations for torque, centripetal acceleration, and rotational kinetic energy. A motor at 3000 RPM has an angular velocity of 314.16 rad/s.
What are common RPM values for everyday devices?
Hard drives spin at 5,400 to 15,000 RPM. Washing machines reach 800-1,600 RPM during spin cycles. Car engines idle at 600-1,000 RPM and redline at 5,000-9,000 RPM. Ceiling fans turn at 100-350 RPM. Dental drills operate at 250,000-400,000 RPM. Jet turbines reach 10,000-25,000 RPM. Each application is optimized for its specific mechanical requirements.
How do I find the period of one revolution from an RPM figure?
The period is the time for a single revolution, so it is 60 divided by the RPM value, or equivalently the reciprocal of the frequency in hertz. A shaft at 3,600 RPM turns at 60 Hz and completes one revolution in 1/60 of a second, about 16.7 milliseconds. Period is the natural quantity when reading an oscilloscope trace or timing a strobe against a rotating mark.
How do I convert RPM into degrees per second or radians per second?
One revolution is 360 degrees, so degrees per second equals RPM times 360 divided by 60, which simplifies to RPM times six. One revolution is also 2 pi radians, so angular velocity in radians per second is RPM times 2 pi divided by 60, roughly RPM times 0.10472. Radians per second is the form used in torque and power equations, where power equals torque times angular velocity.
Why are electric motor speeds tied to the mains frequency?
The rotating field of an AC machine turns at a synchronous speed set by supply frequency and pole count, given by 120 times frequency divided by the number of poles, in RPM. A two-pole machine on a 60 Hz supply therefore has a synchronous speed of 3,600 RPM, and a four-pole machine 1,800 RPM. On a 50 Hz supply the same machines run at 3,000 and 1,500 RPM.
What is slip and why does an induction motor run slower than synchronous speed?
An induction motor must have relative motion between rotor and rotating field to induce rotor current and produce torque, so the rotor always lags the synchronous speed under load. That shortfall, expressed as a fraction of synchronous speed, is called slip. It rises with load, which is why measured shaft RPM sits a little below the synchronous figure and drops further as the machine is worked harder.
How does a gear ratio change the rotational frequency through a drivetrain?
Rotational frequency scales inversely with the gear ratio. A 3:1 reduction turns 3,000 RPM at the input into 1,000 RPM at the output, dividing the frequency by three while multiplying torque by roughly the same factor, less losses. Converting each stage to hertz makes the chain easy to follow, and it is also the form needed when comparing shaft speed against a bearing or vibration frequency.
How do I turn RPM into the linear speed of a wheel or roller?
Multiply the rotational frequency in hertz by the circumference, since one revolution advances the surface by one circumference. Circumference is pi times the diameter, so a 700 mm wheel covers about 2.199 metres per revolution, and at 60 Hz that is roughly 132 metres per second. Use the effective rolling diameter under load rather than the nominal size when accuracy matters.
References
Reviewed for accuracy by Manoj Kumar, Mathematics Educator ยท Editorial policy
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