Helmets & Gear
How to fit a kids bike helmet
Two fingers of gap above the eyebrows, side straps forming a V just below each ear, and no more than one finger under the buckled chin strap. Then shake the head: a correctly fitted helmet moves the eyebrows, not the shell.
The four steps
Step 01
Position: two fingers above the eyebrows
The helmet sits level, not tipped back. The front rim should be about two of your child's finger-widths above their eyebrows. A helmet pushed back exposes the forehead, which is the part that hits things.
Step 02
Tighten the cradle until it stays put
Turn the dial (or adjust the cradle) until the helmet stays in place with the straps still undone. If the helmet only stays on because the chin strap is tight, it is the wrong size.
Step 03
Side straps: a V just below the ear
Adjust the sliders so the front and rear straps meet in a V that sits just below and slightly forward of the earlobe. This is what stops the helmet rotating forward or back.
Step 04
Chin strap: one finger, no more
Buckle it and check you can slide one finger between strap and chin, but not two. Ask them to open their mouth wide — they should feel the helmet pull down slightly.
The shake test
Ask your child to shake their head vigorously, then nod hard. The helmet should move their skin — you will see their eyebrows shift. If the helmet slides independently of their head, go back to step 2.
Re-check it every few months
Kids grow, straps slip, and dials get knocked loose in a backpack. A thirty-second re-check at the start of each season catches it. Add it to the first ride checklist each spring.
The three fit failures we see most
Tipped back
Looks comfortable, exposes the forehead entirely. The most common error and the most consequential.
Straps too loose under the chin
Two or three fingers of slack means the helmet can pivot off in a crash. One finger.
Size chosen by age
Helmet sizes are head circumference, not birthdays. The size chart takes thirty seconds and removes the guesswork.
The picks
Every figure below is the manufacturer's own published spec, linked to the page we read it from, so you can check the one number your decision turns on — here is how we choose.
Quick picks — sorted by head size
| # | Product | Score | Best for | Head | Price |
|---|---|---|---|---|---|
| 1 |  Top pickGiro Scamp MIPS II The XS covers a 45–49 cm head and carries the CPSC certification for age 1 and up with extended rear coverage — the combination most toddler helmets miss. | 9.8/10 | Toddlers and preschoolers | 45–53 cm | |
| 2 |  Bell Sidetrack II MIPS 320 g in youth size with a visor and Mips Evolve — the value pick once a child is past five and riding further than the driveway. | 9.5/10 | School-age riders | 47–57 cm | |
| 3 |  NÜDL Youth MIPS A skate-shape helmet with MIPS inside and a magnetic buckle outside, in graphics kids pick for themselves — which is most of the battle at this age. | 9.5/10 | The helmet they'll actually wear | 52–60 cm |
n/p = the manufacturer does not publish that figure. Every other spec number here comes straight off their spec page. Scores are ours, on the 8.4–9.8 scale explained on our how we choose page.
Top pick — Toddlers and preschoolers
Category-defining · our scale
Giro Scamp MIPS II
The XS covers a 45–49 cm head and carries the CPSC certification for age 1 and up with extended rear coverage — the combination most toddler helmets miss.
| Head size | 45–53 cm |
|---|---|
| Brakes | — |
| Frame | In-mold polycarbonate shell, MIPS liner |
| Brand says | XS is CPSC certified for age 1 and older; S for age 5 and older |
Why we picked it
- XS 45–49 cm, S 49–53 cm — two sizes across the whole toddler-to-kid range
- Extended rear coverage on the XS
- Roc Loc Jr. dial fit with a pinch-guard buckle
Good to knowThe MIPS version costs more than the plain shell, and the dial fit wants a quick re-check at the start of each ride.
How we checked it: Researched from published specs · Giro — Scamp MIPS II
#ad · How we make money · Price as of November 12, 2026
#2 — School-age riders
Category-defining · our scale
Bell Sidetrack II MIPS
320 g in youth size with a visor and Mips Evolve — the value pick once a child is past five and riding further than the driveway.
| Head size | 47–57 cm |
|---|---|
| Brakes | — |
| Frame | In-mold polycarbonate shell, Mips Evolve |
| Brand says | CPSC certified for age 5 and older |
Why we picked it
- Universal Child 47–54 cm and Universal Youth 50–57 cm
- 320 g in size Y, light for a helmet with rotational protection
- Removable visor for trail riding
Good to knowCertified for age 5 and up on universal sizing, so it is the youth pick here rather than the toddler one.
How we checked it: Researched from published specs · Bell — Sidetrack II MIPS
#ad · How we make money · Price as of November 12, 2026
#3 — The helmet they'll actually wear
Category-defining · our scale
NÜDL Youth MIPS
A skate-shape helmet with MIPS inside and a magnetic buckle outside, in graphics kids pick for themselves — which is most of the battle at this age.
| Head size | 52–60 cm |
|---|---|
| Brakes | — |
| Frame | ABS skate-style shell over EPS, with a MIPS liner |
| Brand says | Two youth sizes: YS 52–55 cm and YM 56–60 cm |
Why we picked it
- MIPS in a bucket/skate shell, which most skate-style helmets skip
- Fidlock magnetic buckle: one-handed, and it cannot pinch a chin
- PAS dial fit system for a precise final adjustment
- 11 vents, which a skate shell usually does not have
Good to knowSizing starts at 52 cm, so this is a youth helmet rather than a toddler one, and a skate shell runs warmer than a vented road shape.
How we checked it: Researched from published specs · NÜDL — Youth MIPS helmet
#ad · How we make money · Price as of November 12, 2026
Questions parents actually ask
01How should a kids bike helmet fit?
Level on the head with about two finger-widths above the eyebrows, side straps forming a V just below each ear, and one finger of space under the buckled chin strap. It should move the scalp when the head shakes.
02How tight should a child's helmet strap be?
Tight enough that only one finger fits between the strap and the chin. Have them open their mouth wide — they should feel the helmet pull down.
03Should a bike helmet be tight or loose?
Snug. The helmet should stay in place with the chin strap undone; if it only stays on because the strap is tight, it is too big.
Our recommendation
Top pick
9.8/10Giro Scamp MIPS II
Toddlers and preschoolers. The MIPS version costs more than the plain shell, and the dial fit wants a quick re-check at the start of each ride.
#ad · How we make money · Price as of November 12, 2026
Runner-up
9.5/10Bell Sidetrack II MIPS
School-age riders. Certified for age 5 and up on universal sizing, so it is the youth pick here rather than the toddler one.
#ad · How we make money · Price as of November 12, 2026
Sources
Read next
- Helmets & GearKids helmet size chartHead circumference to helmet size, in one table.
- Helmets & GearBest kids bike helmetsFive helmets, compared on head size and certification.
- Helmets & GearWhen to replace a kids bike helmetAfter an impact, after a growth spurt, after damage.
- Learning to RideFirst ride checklistNine checks, ten minutes, before the first ride.