| Skewness | classification |
| 1 > Sk > 0.3 | very asymmetrical sands towards the ends |
| 0.3 > Sk > 0.1 | Asymmetrical towards the ends |
| 0.1 > Sk > −0.1 | Almost asymmetrical |
| −0.1 > Sk > −0.3 | Asymmetric towards coarse |
| −0.3 > Sk > −1 | Very asymmetrical towards the coarse |