Kids helmet sizes
Ages 1 to 10: heads of 46 to 55 cm
Measure with a tape around the head where the helmet sits: across the forehead, just above the eyebrows and ears. Keep the tape level and read whole centimetres.
The buying rule: the range printed in the helmet must contain the measurement. A 51 cm head gets a helmet marked 48–52, not one marked 52–56. If two helmets fit, take the smaller: the dial tightens inward, never outward.
A helmet gets no growing room. Hats are bought to grow into; a helmet that wobbles sits wrong at the exact moment it is needed. Right size today, new helmet when the head outgrows the range.
Head circumference and helmet size by age
| Age | Head (cm) | Typical helmet label (cm) |
|---|---|---|
| 1 yrs | 46–48 | 44–48 |
| 2 yrs | 48–50 | 48–52 |
| 3 yrs | 49–51 | 48–52 |
| 4 yrs | 50–52 | 48–52 |
| 5 yrs | 50–52 | 48–52 |
| 6 yrs | 51–53 | 48–52 |
| 7 yrs | 51–53 | 48–52 |
| 8 yrs | 52–54 | 52–56 |
| 9 yrs | 52–54 | 52–56 |
| 10 yrs | 53–55 | 52–56 |
Labels vary between makers; the column shows the most common span. The measurement decides, not the age.
Two quick answers
What helmet size does a 3-year-old wear?
A typical head at age 3 is 49 to 51 cm, which usually means a helmet marked 48–52. Measure first: the range must contain the number.
Should kids grow into a helmet?
No. A loose helmet slides out of place in a fall. Buy the one that fits today and adjust with the rear dial; when the head outgrows the range, it is time for the next one.
Keep reading
Sources
Checked against the sources below on August 10, 2026.