How do I convert RPM to Hz?

Divide RPM by 60. For example, 3000 RPM = 3000/60 = 50 Hz. This gives the fundamental (1×) frequency. Hz means cycles per second, while RPM means revolutions per minute.

What are harmonics in vibration analysis?

Harmonics are integer multiples of the fundamental (1×) frequency. The 2× harmonic is twice the fundamental, 3× is three times, etc. Different fault types generate specific harmonic patterns — for example, misalignment often shows strong 2× components.

What does the 1× vibration frequency indicate?

The 1× frequency corresponds to one event per revolution. The most common source of 1× vibration is mass unbalance. Other 1× sources include bent shaft, eccentric rotor, and resonance excited at running speed.

Why are higher harmonics important?

Higher harmonics help diagnose specific faults: 2× often indicates misalignment or looseness, blade/vane pass frequency is the number of blades × RPM, gear mesh frequency is the number of teeth × RPM. Each harmonic pattern points to a specific root cause.

What is the difference between Hz, CPM, and orders?

Hz (Hertz) = cycles per second. CPM (Cycles Per Minute) = Hz × 60 = same value as RPM for 1× order. Orders are multiples of the shaft speed: 1× = one per revolution, 2× = two per revolution, etc. Orders are speed-independent, while Hz/CPM change with RPM.

Free Engineering Tool · #008

Harmonic Frequency Calculator

Convert RPM to Hz and display harmonics 1× through 20×. Essential for vibration analysis and machine diagnostics.

RPM → Hz 1×–20× Orders Hz & CPM

Results

1× Fundamental Frequency

—

Period (1× cycle)

—

Angular Velocity ω

—

Order	Frequency (Hz)	CPM	Period (ms)

RPM to Hz Conversion

The fundamental frequency (1× order) in Hz equals the rotational speed divided by 60:

Harmonic Frequencies

Each harmonic (order) is an integer multiple of the fundamental frequency:

where n is the harmonic order (1, 2, 3, …).

Angular Velocity

Common Harmonic Sources in Vibration

Order	Common Source
1×	Unbalance, bent shaft, eccentricity
2×	Misalignment (angular/parallel), looseness
3×	Misalignment (severe), looseness
N×	Blade/vane pass (N = number of blades)
Z×	Gear mesh frequency (Z = number of teeth)
½×	Oil whirl, rubbing
0.43×	Oil whip

Practical Example

Example — 3000 RPM Motor

Given: Speed = 3000 RPM

1× = 3000 / 60 = 50 Hz (3000 CPM)

2× = 2 × 50 = 100 Hz (6000 CPM)

3× = 3 × 50 = 150 Hz (9000 CPM)

Period = 1 / 50 = 20 ms

ω = 2π × 50 = 314.16 rad/s

💡 Tip: In vibration analysis, the harmonic spectrum pattern is a key diagnostic tool. Unbalance shows a dominant 1× peak, misalignment shows strong 2× (and sometimes 3×), and bearing defects generate non-synchronous frequencies related to bearing geometry.