What is vibration velocity?

Vibration velocity is the speed at which a vibrating surface moves back and forth, measured in mm/s RMS. It is the most widely used parameter for evaluating machine condition because it correlates well with vibration energy and bearing/structural damage. ISO 10816 and ISO 20816 define permissible limits based on machine class.

What is the difference between ISO 10816 and ISO 20816?

ISO 20816 is the modern replacement for ISO 10816. The zone boundaries and machine classes are essentially the same for most non-rotating parts (housing) vibration evaluation. ISO 20816 adds shaft vibration requirements and updated measurement practices. For broadband velocity RMS evaluation on machine housings, the classic ISO 10816 limits still apply.

How do I measure vibration velocity?

Vibration velocity is measured with an accelerometer or velocity sensor mounted on the machine bearing housing. The sensor signal is processed by a vibration analyzer or portable instrument to produce a broadband RMS velocity value in mm/s. Measurements should be taken in three directions: horizontal, vertical, and axial.

What should I do if the machine is in Zone C or D?

Zone C means the vibration level is tolerable only for limited periods — plan corrective action. Zone D means the vibration is severe enough to cause damage — stop the machine immediately if possible and investigate root cause. Common corrective actions include re-balancing, alignment correction, bearing replacement, or addressing structural resonance.

Which sensor is best for vibration velocity measurement?

For most industrial machines, a piezoelectric accelerometer with integrated electronics (IEPE/ICP type) is the standard choice. The acceleration signal is electronically integrated to velocity. For low-frequency applications below 10 Hz, electrodynamic velocity sensors may be preferred. Ensure the sensor frequency range covers 10-1000 Hz per ISO 10816.

Free Engineering Tool

Permissible Vibration Velocity (ISO 10816)

Look up permissible vibration velocity limits per ISO 10816 / ISO 20816. Select machine class, enter measured velocity to get zone evaluation A/B/C/D.

ISO 10816 ISO 20816 Zones A / B / C / D

Results

Zone Evaluation

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Machine Class

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Measured Velocity

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Equivalent (in/s)

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Zone	Velocity Range	Meaning

Vibration Velocity RMS

The vibration velocity RMS value is related to peak velocity by:

v_RMS — root mean square vibration velocity (mm/s)
v_peak — peak vibration velocity (mm/s)

ISO 10816 evaluates machine vibration severity based on broadband v_RMS (typically 10–1000 Hz). Machines are classified into four groups, and each group has four evaluation zones (A, B, C, D).

ISO 10816 Zone Boundaries — All Classes

Zone	Class I (≤15 kW)	Class II (15–75 kW)	Class III (rigid, >75 kW)	Class IV (flexible, turbo)
A (New)	≤ 0.71	≤ 1.12	≤ 1.8	≤ 2.8
B (Acceptable)	0.71 – 1.8	1.12 – 2.8	1.8 – 4.5	2.8 – 7.1
C (Tolerable)	1.8 – 4.5	2.8 – 7.1	4.5 – 11.2	7.1 – 18
D (Damaging)	> 4.5	> 7.1	> 11.2	> 18

All values in mm/s RMS.

Practical Example

Example — 45 kW Motor (Class II)

Given: Measured vibration velocity = 3.2 mm/s RMS

Class II boundaries: A ≤ 1.12, B ≤ 2.8, C ≤ 7.1, D > 7.1

3.2 mm/s exceeds B boundary (2.8) but is below C boundary (7.1)

Result: Zone C — Tolerable for limited periods only. Plan corrective action.

ISO 10816 Vibration Velocity Limits — Zone Calculator

Published by Nikolai Shelkovenko on February 15, 2026 May 25, 2026

Results

Vibration Velocity RMS

ISO 10816 Zone Boundaries — All Classes

Practical Example

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