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ISO 4406 Oil Cleanliness Code from Particle Counts
What ISO 4406 cleanliness code do these particle counts give, and does the oil meet its target?
ISO 4406 range numbers for particles of 4, 6 and 14 µm and larger per millilitre of oil, from counts per millilitre or per sample volume, with the three-part code and a check against a target code for each size.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Sample volume counted | mL | Volume of oil the counts refer to (1 mL if counts are already per millilitre). |
| Particles ≥ 4 µm in the sample | Count of particles 4 µm(c) and larger. | |
| Particles ≥ 6 µm in the sample | Count of particles 6 µm(c) and larger. | |
| Particles ≥ 14 µm in the sample | Count of particles 14 µm(c) and larger. | |
| Target code | ||
| Target range number, 4 µm | Target range number at 4 µm (from the machine or component maker). | |
| Target range number, 6 µm | Target at 6 µm. | |
| Target range number, 14 µm | Target at 14 µm. | |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Sample volume counted
- What it is
- The volume of oil that the three particle counts were taken from. The tool divides each count by it to get particles per millilitre.
- Units and format
- Enter a number in mL: mL. The form accepts 0.000001 mL to 100000 mL. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1 mL as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger volume lowers the counts per millilitre, so the range numbers fall.
- Get it right
- If your counter already reports particles per millilitre, leave this at 1 mL; per 100 mL reports need 100.
What this means: Particles ≥ 4 µm in the sample
- What it is
- The number of particles 4 µm(c) and larger found in the sample volume. It sets the first number of the ISO 4406 code.
- Units and format
- Enter a plain number with no unit. The form accepts 0 or more. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 15000 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- This is a cumulative count, so it includes all the larger particles too and must be the largest of the three.
What this means: Particles ≥ 6 µm in the sample
- What it is
- The number of particles 6 µm(c) and larger in the same sample volume. It sets the middle number of the code.
- Units and format
- Enter a plain number with no unit. The form accepts 0 or more. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3000 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Cumulative: it must not be smaller than the 14 µm count or larger than the 4 µm count.
What this means: Particles ≥ 14 µm in the sample
- What it is
- The number of particles 14 µm(c) and larger in the same sample volume. It sets the last number of the code.
- Units and format
- Enter a plain number with no unit. The form accepts 0 or more. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1000 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use counts sized to ISO 11171 µm(c); older calibrations use different size steps.
Target code
What this means: Target range number, 4 µm
- What it is
- The highest range number you accept at 4 µm, the first number of the target cleanliness code set by the machine or component maker.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 30. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 18 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take targets from the hydraulic component or lubricant specification; the oil passes only when it is at or below each target.
What this means: Target range number, 6 µm
- What it is
- The highest range number you accept at 6 µm, the middle number of the target cleanliness code.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 30. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 16 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Each step down in range number halves the allowed particle count.
What this means: Target range number, 14 µm
- What it is
- The highest range number you accept at 14 µm, the last number of the target cleanliness code.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 30. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 13 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Write the target in the same order as the result, for example the code 18/16/13 gives targets 18, 16 and 13.
Method and formulas
- Counts are converted to particles per millilitre.
- Range numbers double with each step: number R covers more than 0.01 × 2^(R−1) up to 0.01 × 2^R particles per mL, so R = ⌈log₂(count per mL ÷ 0.01)⌉.
- The code is written R₄/R₆/R₁₄, for example 21/19/17.
- Example: 15000, 3000 and 1000 particles per mL give ISO 21/19/17.
Limitations
- Counts must come from a calibrated counter per ISO 11171 sizes µm(c).
- Range numbers above 28 or below 1 are reported at the limit as calculated.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Turn a particle count report into an ISO code
- Check oil against the target cleanliness for a machine
- Track filtration improvements over time
Who it is for
- Reliability engineers
- Lubrication technicians
- Maintenance engineers
What you get
- ISO code (4/6/14 µm)
- Count per millilitre for each size
- Comparison with the target
Interpreting the result
- Each range number down halves the particle count; one step cleaner can noticeably extend component life.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2439–2441. Topic reference; no source tables or recommended settings are reproduced.
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Open the ISO 4406 Oil Cleanliness Code from Particle Counts calculator