An electric motor runs at 1,500 RPM. What frequency should I program my VFD to output?

1,500 RPM ÷ 60 = 25 Hz. Set the variable frequency drive to 25 Hz output for a 2-pole motor. For a 4-pole motor that runs at 1,500 RPM on a 50 Hz grid, that 50 Hz input is correct. Always check the motor's pole count before programming a VFD.

Why does a 2-pole motor running on 60 Hz power spin at exactly 3,600 RPM?

The motor's magnetic field rotates at 60 cycles per second (60 Hz), pulling the rotor along with it. 60 rotations per second × 60 seconds per minute = 3,600 RPM. That is why AC generators are also designed to spin at exactly 3,600 RPM — they must output 60 Hz to keep the grid in sync.

My fan is rated 1,200 RPM. How many times per second does the blade pass a fixed point?

1,200 RPM ÷ 60 = 20 Hz — 20 complete rotations per second. If the fan has 3 blades, the blade-pass frequency is 20 × 3 = 60 Hz, which is why some fans produce a 60 Hz hum that resonates with lighting or other 60 Hz grid devices.

Is there a quick mental conversion from RPM to Hz?

Divide by 60. Shortcuts: 60 RPM = 1 Hz, 120 RPM = 2 Hz, 600 RPM = 10 Hz, 1,200 RPM = 20 Hz, 3,600 RPM = 60 Hz. Once you have Hz, convert to kHz or higher with [Hz to kHz](/frequency/hz-to-khz/).

RPM to Hz Converter

Enter a value to instantly convert between frequency units.

From

Precision4 dp

1 RPM = 0.0167 Hertz

Key Formulas

Hertz → Kilohertz

kHz = Hz × 0.001

Kilohertz → Hertz

Hz = kHz × 1000

Megahertz → Gigahertz

GHz = MHz × 0.001

Gigahertz → Megahertz

MHz = GHz × 1000

Formula

Hz = RPM ÷ 60

RPM measures mechanical rotation speed — how many complete turns per minute. Hertz measures frequency — cycles per second. Because there are 60 seconds in a minute, the conversion is simply dividing RPM by 60. This matters when matching motor speed to power grid frequency, setting variable frequency drives, or analysing vibration spectra with FFT software that works in Hz. An AC motor at 3,000 RPM spins at 50 Hz — exactly the European mains frequency it's designed to run on.

Source: NIST SP 811, Table B.8

Last reviewed: 2026-06-11 · see our methodology

Frequently Asked Questions

Real-World Examples

2-pole AC motor synchronous speed in a 60 Hz grid (North America). Power stations generate AC at exactly 60 Hz by spinning their rotors at 3,600 RPM.

3600 rpm = 60 Hz

2-pole AC motor synchronous speed in a 50 Hz grid (Europe, Asia). The motor shaft spins at exactly 50 rotations per second at synchronous speed.

3000 rpm = 50 Hz

Typical 4-pole induction motor running at 1,450 RPM under load (synchronous is 1,500 RPM at 50 Hz). The 50 Hz grid minus 3.3% slip gives this real-world speed.

1450 rpm = 24.17 Hz

Hard drive platter at 7,200 RPM rotates at 120 Hz. Vibration analysis of a drive uses this frequency as the fundamental mechanical signature in FFT spectra.

7200 rpm = 120 Hz

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RPM to Hz Converter

Key Formulas

Formula

Frequently Asked Questions

Real-World Examples

Related Converters