Hydraulic Oil Cleanliness: A Comparison Table of ISO Standards and NAS 1638 Standards
| ISO Code | NAS 1638 |
| 19/16 | 10 |
| 18/15 | 9 |
| 17/14 | 8 |
| 16/13 | 7 |
| 15/12 | 6 |
| 14/12 | |
| 14/11 | 5 |
| 13/10 | 4 |
| 12/9 | 3 |
| 11/8 | 2 |
| 10/8 | |
| 10/7 | 1 |
| 10/6 | |
| 9/6 | 0 |
ISO 4406 Cleanliness Standard
| Particles > 5 μm, Particles > 15 μm | ISO Grade | |
| 100 CC Hydraulic Oil | ||
| 8,000,000 | 16,000,000 | 24 |
| 4,000,000 | 8,000,000 | 23 |
| 2,000,000 | 4,000,000 | 22 |
| 1,000,000 | 2,000,000 | 21 |
| 500,000 | 1,000,000 | 20 |
| 250,000 | 500,000 | 19 |
| 130,000 | 250,000 | 18 |
| 64,000 | 130,000 | 17 |
| 32,000 | 64,000 | 16 |
| 16,000 | 32,000 | 15 |
| 8,000 | 16,000 | 14 |
| 4,000 | 8,000 | 13 |
| 2,000 | 4,000 | 12 |
| 1,000 | 2,000 | 11 |
| 500 | 1,000 | 10 |
| 250 | 500 | 9 |
| 130 | 250 | 8 |
| 64 | 130 | 7 |
| 32 | 64 | 6 |
| 16 | 32 | 5 |
| 8 | 16 | 4 |
| 4 | 8 | 3 |
| 2 | 4 | 2 |
| 1 | 2 | 1 |
