ISO 14644-1 Cleanroom Classification Calculator: Sampling Locations and Particle Limits
Enter the cleanroom area, the target ISO class and the particle sizes you classify at. The calculator gives the minimum number of sampling locations, the class limits and the minimum sample volume and time at each location, following ISO 14644-1:2015.
Engineering estimate only. Confirm by testing and validation for your equipment and load.
How the calculation works
1. Number of sampling locations
ISO 14644-1:2015 sets the minimum number of sampling locations, NL, from the area of the cleanroom or clean zone in Table A.1. If the area falls between two values in the table, the next larger value is used. Above 1,000 m², NL = 27 × (A / 1,000), rounded up. For unidirectional airflow, the area may be taken as the cross-section of the moving air perpendicular to the direction of flow.
| Area up to (m²) | Locations | Area up to (m²) | Locations |
|---|---|---|---|
| 2 | 1 | 76 | 15 |
| 4 | 2 | 104 | 16 |
| 6 | 3 | 108 | 17 |
| 8 | 4 | 116 | 18 |
| 10 | 5 | 148 | 19 |
| 24 | 6 | 156 | 20 |
| 28 | 7 | 192 | 21 |
| 32 | 8 | 232 | 22 |
| 36 | 9 | 276 | 23 |
| 52 | 10 | 352 | 24 |
| 56 | 11 | 436 | 25 |
| 64 | 12 | 636 | 26 |
| 68 | 13 | 1,000 | 27 |
| 72 | 14 | > 1,000 | 27 × A / 1,000 |
The room is divided into NL sections of roughly equal area and one location is placed in each section, at working height unless the protocol says otherwise.
2. Class limits
The maximum concentration for class N at particle size D (µm) comes from Cn = 10N × (0.1 / D)2.08, rounded as in Table 1 of the standard. The calculator uses the Table 1 values for ISO 4 to ISO 9:
| Class | ≥ 0.1 µm | ≥ 0.2 µm | ≥ 0.3 µm | ≥ 0.5 µm | ≥ 1 µm | ≥ 5 µm |
|---|---|---|---|---|---|---|
| ISO 4 | 10 000 | 2 370 | 1 020 | 352 | 83 | – |
| ISO 5 | 100 000 | 23 700 | 10 200 | 3 520 | 832 | – |
| ISO 6 | 1 000 000 | 237 000 | 102 000 | 35 200 | 8 320 | 293 |
| ISO 7 | – | – | – | 352 000 | 83 200 | 2 930 |
| ISO 8 | – | – | – | 3 520 000 | 832 000 | 29 300 |
| ISO 9 | – | – | – | 35 200 000 | 8 320 000 | 293 000 |
Particles per cubic metre of air, at and above the stated size. A dash means the standard does not give a limit for that size and class.
3. Sample volume and time
Each location gets at least one sample, large enough that at least 20 particles would be counted if the concentration were exactly at the class limit for the largest particle size considered:
Vs in litres; Cn,m = class limit (particles/m³) for the largest size considered. Each sample is at least 2 L and at least 1 minute.
Dividing by the particle counter's flow rate gives the sampling time per location.
4. Acceptance
The room meets the class if the average concentration at each location is at or below the class limit for every size considered. The 2015 edition removed the 95% upper confidence limit calculation that the 1999 edition required for 2 to 9 locations.
EU GMP Annex 1 grades
For classification, EU GMP Annex 1 relates its grades to ISO classes at ≥ 0.5 µm:
| Grade | At rest | In operation |
|---|---|---|
| A | ISO 5 | ISO 5 |
| B | ISO 5 | ISO 7 |
| C | ISO 7 | ISO 8 |
| D | ISO 8 | Not predetermined |
Annex 1 also sets its own limits for ≥ 5.0 µm particles, and its own requirements for sampling. Check Annex 1 directly when classifying a GMP cleanroom. More on the standard: ISO 14644-1 cleanroom classification and EU GMP Annex 1.
Limits of this calculator
- It gives the minimum required by ISO 14644-1. Your protocol, risk assessment or a regulator may require more locations or larger samples.
- It covers classification, not routine monitoring, which is planned separately under ISO 14644-2.
- Intermediate classes (for example ISO 6.5) and sizes other than those listed are not included.
- Locations must still be placed sensibly — near critical points, not only on a grid.
Common questions
How many sampling locations does ISO 14644-1 require?
It depends on the area. ISO 14644-1:2015 Table A.1 gives the minimum: for example 6 locations up to 24 m², 10 up to 52 m² and 27 up to 1,000 m². Above 1,000 m² the number is 27 × area / 1,000, rounded up.
How do I calculate the minimum sample volume?
Vs = (20 / Cn,m) × 1000 litres, where Cn,m is the class limit for the largest particle size considered. Each sample must also be at least 2 litres and at least 1 minute long.
What is the ISO 7 limit at 0.5 µm?
352 000 particles per cubic metre at and above 0.5 µm. At 5 µm the ISO 7 limit is 2 930 per cubic metre.
Does ISO 14644-1:2015 still use the 95% UCL?
No. The 2015 edition removed the 95% upper confidence limit. Each location must meet the class limit on its own.
Send your numbers to an engineer
Use the button under the result to fill this form, or describe your space and equipment. An engineer reviews it and replies.
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