Reference chart
Helmet size chart by age and head circumference
Measure head circumference about 1 in above the eyebrows: under 51 cm is usually XS (toddler), 51 to 55 cm small, 55 to 59 cm medium, 59 to 63 cm large. A typical 2 year old measures 48 cm, a 5 year old 51 cm, an 8 year old 52.5 cm and a 12 year old 54.5 cm.
| Size | Head circumference | Inches |
|---|---|---|
| XXS (infant/toddler) | 44 to 48 cm | 17.3 to 18.9 in |
| XS (toddler) | 47 to 51 cm | 18.5 to 20.1 in |
| S | 51 to 55 cm | 20.1 to 21.7 in |
| M | 55 to 59 cm | 21.7 to 23.2 in |
| L | 59 to 63 cm | 23.2 to 24.8 in |
| XL | 61 to 65 cm | 24.0 to 25.6 in |
| Age | Typical head | Usual size | Guide |
|---|---|---|---|
| 1 | 46 cm | XXS (infant/toddler) | Age 1 |
| 2 | 48 cm | XS (toddler) | Age 2 |
| 3 | 49.5 cm | XS (toddler) | Age 3 |
| 4 | 50.5 cm | XS (toddler) | Age 4 |
| 5 | 51 cm | S | Age 5 |
| 6 | 51.5 cm | S | Age 6 |
| 7 | 52 cm | S | Age 7 |
| 8 | 52.5 cm | S | Age 8 |
| 9 | 53 cm | S | Age 9 |
| 10 | 53.5 cm | S | Age 10 |
| 11 | 54 cm | S | Age 11 |
| 12 | 54.5 cm | S | Age 12 |
| Standard | What it means |
|---|---|
| CPSC | the US federal standard every bicycle helmet sold in the US must meet. Single-impact. |
| ASTM F1492 | the skateboard and trick-skating standard. Tested for multiple lower-energy impacts, which is what skatepark falls look like. |
| NTA 8776 | Dutch standard for speed pedelecs up to 28 mph (45 km/h), with higher-energy impact tests and more coverage. |
| ASTM F1952 | downhill mountain-bike full-face standard, including a chin-bar test. |
| DOT (FMVSS 218) | the US motorcycle helmet standard. Heavier and hotter, but rated for motor-vehicle speeds. |
CONVENTION: match the helmet to the speed. Under about 15 mph a CPSC bike helmet; skatepark riding a dual CPSC plus ASTM F1492 helmet; 20 mph and up an NTA 8776 or full-face helmet; 28 mph and up a full-face, and many riders of 30+ mph scooters choose DOT.
Wear a helmet every ride, and check your state and city rules on age, speed and where scooters may ride. This page is researched guidance, not professional, legal or medical advice. Specifications come from each product listing and can change; confirm on the listing before you buy.