| Bell Sports Helmet Sizing | Hat Size | Circumference in inches | European Sizing |
| S - Small if 3 sizes are made | 6 5/8 - 7 | 20 7/8" - 22" | 53 - 56 cm |
| M - Medium if 3 sizes are made | 7 - 7 3/8 | 22" - 23 1/4" | 56 - 59 cm |
| L - Large if 3 sizes are made | 7 1/4 - 7 5/8 | 22 7/8" - 24" | 58 - 61 cm |
| S/M - Sml/Med if 2 sizes are made | 6 3/4 - 7 1/8 | 21 1/4"" - 22 3/8" | 54 - 57 cm |
| M/L - Med/Lrg if 2 sizes are made | 7 1/4 - 7 5/8 | 22 7/8" - 24" | 58 - 61 cm |
