Scoring algorithm for the RSI
| Predominant radiological pattern in the lung zone | Pattern score | Extent of volumetric radiological involvement (%) | Volumetric score |
| Normal lung | 1 | 0 (normal) | 0 |
| Ground glass opacities | 2 | 1–24 | 1 |
| Consolidation | 3 | 25–49 | 2 |
| 50–74 | 3 | ||
| 75–100 | 4 | ||
Radiologic Severity Index (RSI) scores are calculated by multiplying the predominant pattern for each lung zone by the extent of volumetric radiological involvement for that zone. The sum of scores from all six zones gives the final RSI, ranging from 0 to 72.