ISO 10816 / 20816 Vibration Converter
Convert a vibration amplitude between acceleration (g), velocity (mm/s), and displacement (µm), and between peak, RMS, and peak-to-peak, at a given frequency. It gets field readings into the mm/s RMS that ISO 10816 / 20816 severity limits use.
Tool Purpose & Notes
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Input
Enter a value to convert.
Peak, RMS, and peak-to-peak: three ways to measure one wave
A vibrating point traces a wave over time. There is only one wave, but three common ways to put a single number on its size. They are all just distances measured on the same picture:
One wave, three measurements. Peak is rest-to-crest; peak-to-peak is the full swing (crest to trough) and is always exactly twice the peak; RMS is the "energy-equivalent" average, which for a sine is 0.707 × peak.
- Peak (0-to-peak): the amplitude, from rest to the crest. This is the "true" size the physics uses.
- Peak-to-peak: the full top-to-bottom swing. Always
2 × peak. Common for displacement (e.g. shaft µm pk-pk). - RMS: root-mean-square, the energy-equivalent average. For a sine,
peak / √2 ≈ 0.707 × peak. Common for velocity (ISO 20816 mm/s RMS).
Which setting should I use?
There's no universal "correct" convention. Use whatever your instrument, standard, or spec sheet uses, so the numbers stay comparable. In practice each pairs with a quantity:
| Convention | Usually paired with | Why / where you'll see it |
|---|---|---|
| Peak-to-peak | Displacement (µm, mil) | Shaft/relative motion from proximity probes; you compare total travel against bearing clearances (API 670). |
| RMS | Velocity (mm/s) | The default for overall machine-vibration severity; it tracks vibration energy, so it correlates best with fatigue and damage (ISO 20816 / 10816). |
| Peak (0-to-peak) | Acceleration (g) | Bearing and gear defects and shocks, where the worst instantaneous spike matters more than the average. |
And the quantity itself is usually chosen by frequency band, because ω2 weighting makes each most sensitive in a different range:
| Quantity | Best frequency band | Typical use |
|---|---|---|
| Displacement | Low (below ~10 Hz) | Shaft position, slow large motions, balancing, structural sway. |
| Velocity | Mid (~10–1000 Hz) | General rotating-machine health and severity; the usual choice for ISO 20816 checks. |
| Acceleration | High (above ~1 kHz) | Rolling-element bearing and gear-mesh defects, high-frequency content. |
Rule of thumb: if you're unsure, machine-health work is almost always velocity, mm/s RMS (ISO 20816). Reach for displacement pk-pk on slow shafts and acceleration g-peak on bearings.
Why one setting moves every number
A bare "10 mm/s" doesn't describe a real vibration until you say which convention it's in. The same 10 is three different signals:
10 mm/s peak → amplitude 10.10 mm/s peak-to-peak → the full swing is 10, so the amplitude is only 5 (half the size).10 mm/s RMS → the amplitude is 10 × √2 ≈ 14.1 (larger).
A peak-to-peak of 10 is half the amplitude of a peak of 10, and an RMS of 10 is larger than both. Shrink the signal and its displacement, velocity, and acceleration all drop with it, so one dropdown rescales every quantity at once. Each result card lists all three conventions with your entry marked, so the ×2 and ÷√2 steps stay in view.
How the three quantities relate
Once the amplitude is pinned down, displacement, velocity, and acceleration are locked together by the frequency. With angular frequency ω = 2πf:
where:
- \(f\) is the vibration frequency (Hz), the number of cycles per second
- \(\omega\) is the angular frequency (rad/s), equal to \(2\pi f\)
- \(d_{pk}\) is the displacement amplitude, zero-to-peak (m)
- \(v_{pk}\) is the velocity amplitude, zero-to-peak (m/s)
- \(a_{pk}\) is the acceleration amplitude, zero-to-peak (m/s²)
Because acceleration scales with ω², the same displacement produces far higher acceleration at high frequency. That's why accelerometers dominate high-frequency work and proximity probes dominate low-frequency shaft measurement.