Vibration Severity Checker
Enter a measured RMS vibration velocity (mm/s or in/s), choose the machine class, and see which ISO 2372:1974 severity zone it falls in — A Good, B Acceptable, C Unsatisfactory or D Unacceptable — on a colour-coded gauge. A built-in single-frequency converter relates displacement, velocity and acceleration.
⚠ This needs a velocity from a calibrated accelerometer or vibrometer measured over the broadband 10–1000 Hz range. Do not feed it a number from a microphone tool — the mic-based analyzers on this site capture airborne sound and reveal frequency content only; they do not give a calibrated amplitude in mm/s velocity or g, so they cannot be used for ISO severity. The zone tables below are the published ISO 2372:1974 values (the basis of the later ISO 10816 / ISO 20816 series) — verify you have picked the correct machine class and that your instrument reports RMS velocity. The d↔v↔a converter assumes pure single-frequency sinusoidal motion. Everything runs in your browser.
Single-frequency unit converter
For a pure sinusoid at one frequency, displacement, velocity and acceleration are linked by vpeak = 2·π·f·Dpeak and apeak = 2·π·f·vpeak; the velocity field shows RMS = vpeak / √2. Enter a frequency and any one amplitude; the highlighted field drives the others. (Real vibration is rarely a single tone — this is for converting a single spectral line, not an overall level.)
Reference table — ISO 2372 severity zones (mm/s RMS)
How It Works
Vibration severity is judged from the RMS velocity of a machine’s casing or bearing housing, measured over a broad frequency band (10–1000 Hz). Velocity is used because, across that range, it correlates well with the destructive energy of vibration regardless of frequency. The classic ISO 2372:1974 chart sorts machines into four classes by size and mounting, and for each class defines three boundaries that split the velocity scale into four zones: A (good, as just commissioned), B (acceptable for long-term running), C (unsatisfactory — investigate and plan a repair) and D (unacceptable — risk of damage). You read your overall RMS velocity off a calibrated instrument, pick the matching class, and the value lands in one zone. The tool reproduces the published boundaries exactly and places your reading on the colour gauge so you can see how close it is to the next zone.
The single-frequency converter uses the kinematics of pure sinusoidal motion. For a sinusoid at frequency f, peak velocity is Vpeak = 2πf·Dpeak and peak acceleration is Apeak = 2πf·Vpeak, where D is the peak displacement. We convert displacement to peak-to-peak micrometres, velocity to RMS mm/s (RMS = peak / √2 for a sinusoid) and acceleration to peak g (1 g = 9.80665 m/s²). That conversion is exact only for a single tone — a real vibration spectrum has many lines, so use it to convert one spectral component, not an overall broadband level.
The honest limit is the input. ISO severity assumes a properly mounted, calibrated accelerometer or velocity transducer and the correct measurement band; it is not something a microphone can supply. A mic hears the airborne sound a machine radiates, which is useful for spotting which frequencies are present (so you can match them against calculated bearing, gear, imbalance or blade-pass frequencies) but tells you nothing about the true vibration amplitude in mm/s or g. For real condition monitoring against ISO zones, you need an accelerometer and a vibration analyzer, and you must confirm the machine class and that your reading is RMS velocity over the standard band.