A 4-year-old usually needs a 14-inch bike, and if they're taller than about 3 ft 6 in (106-108 cm), a 16" bike. Most kids this age are between 3 ft 1 in and 3 ft 8 in (95-111 cm), right where the two sizes overlap.
- Typical height
- 3′5″ 103 cm; range 3′1″–3′8″ (95–111 cm)
- Their bike
- 14" or 16-inch
- Bike weight
- < 10.7 lb 4.9 kg: 30% of about 36 lb (16 kg)
Calculate with their exact height
How tall is a 4-year-old?
According to the World Health Organization (WHO), half of 4-year-old boys are taller than 40.7 in (103.3 cm) and half of girls are taller than 40.4 in (102.7 cm). Between the 3rd and 97th percentiles (94% of kids) the range is wide: from 3′1″ to 3′8″ (95-111 cm). In the US, the CDC growth charts give a median of 40.2 in (102.2 cm) for boys and 39.7 in (100.8 cm) for girls. That's why age is a guide, but height is what decides the bike: measure your child barefoot against a wall before you buy.
| 3rd percentile | Median | 97th percentile | |
|---|---|---|---|
| Boys | 37.6 in (95.4 cm) | 40.7 in (103.3 cm) | 43.8 in (111.2 cm) |
| Girls | 37.2 in (94.6 cm) | 40.4 in (102.7 cm) | 43.6 in (110.8 cm) |
What size bike they need
14" bikes fit kids from 3 ft to 3 ft 7 in (92-110 cm) and 16" bikes from 3 ft 4 in to 3 ft 11 in (102-120 cm). In the overlap (3 ft 4 in-3 ft 7 in / 102-110 cm), pick the 16" only if they already pedal confidently or have long legs; if it's their first pedal bike, the 14" will give them more confidence because they'll reach the ground more easily. A practical number: the seat on Woom's 16" bike doesn't go below 19 in (48.2 cm), and on its 14", 15.5 in (39.4 cm). If your child's inseam falls between those two numbers, the 14" is the one.
| Size | Height | Inseam |
|---|---|---|
| 14-inch | 3′0″–3′7″ (92–110 cm) | 15–19 in (38–48 cm) |
| 16-inch | 3′4″–3′11″ (102–120 cm) | 17–22 in (44–55 cm) |
How to check the fit
Seated, they should touch the ground with the toes of both feet (on a first pedal bike, better with the balls of the feet). With the pedal at the bottom, the leg is slightly bent. Check that they can reach the brake levers and squeeze them with two fingers without letting go of the handlebar. Recheck the seat height every three or four months: at this age kids grow about 3 in (7 cm) a year.
Ideal bike weight
A 4-year-old weighs about 36 lb (16 kg). The 30% rule gives under 11 lb (5 kg) of bike. That's hard to meet: the Woom GO 2 (14") weighs 11 lb (5 kg) and the GO 3 (16"), 11.9 lb (5.4 kg) without pedals, while the Btwin 100 14" weighs 16.3 lb (7.4 kg). Every extra pound shows on hills and when they pick the bike up after a fall.
Brakes: coaster brake or hand brakes
Two options: a rear coaster brake plus a front lever, or two hand brakes. Decathlon fits its 14" and 16" Btwin bikes with a lever and a rear drum brake; Woom only uses levers, with a short reach for small hands. What matters is that the levers can be adjusted closer to the bar and that your child can brake hard: try it in the store.
Gears
They don't need them. Almost all 14" and 16" bikes are single-speed (Woom has a 16" version with a two-speed automatic hub, but it isn't necessary).
Training wheels or a balance bike
If they already ride a balance bike, they'll be pedaling without training wheels in an afternoon or two. If they've never ridden, try taking the pedals off the new bike and lowering the seat: they'll use it as a balance bike for a few weeks, then you put the pedals back on. If you still prefer training wheels, take them off as soon as they pedal confidently.
What to look for when you buy
- Measure inseam and height: between 3 ft 4 in and 3 ft 7 in (102-110 cm), both 14" and 16" work.
- Weight: as close to 11 lb (5 kg) as possible.
- Adjustable-reach levers for small hands.
- A fully enclosed chain guard and a padded stem cap.
- Tires with some tread if they'll ride on dirt.
Frequently asked questions
What size bike for a 4-year-old?
14 inches if they're shorter than about 3 ft 6 in (106 cm) or it's their first pedal bike; 16 inches if they're taller and already pedal.
Does a 4-year-old need training wheels?
No. If they already ride a balance bike, they'll move to pedaling without them. If not, take the pedals off their bike for the first few weeks so they learn to balance.
Should I buy a 16-inch bike so it lasts longer?
Only if they can touch the ground with their toes with the seat all the way down. Otherwise they'll be scared and learn later.
Sources
- WHO: Height-for-age, boys 2 to 5 years (percentiles)
- WHO: Height-for-age, girls 2 to 5 years (percentiles)
- WHO: Height-for-age, boys 5 to 19 years (percentiles)
- WHO: Height-for-age, girls 5 to 19 years (percentiles)
- CDC: Growth charts data tables, stature-for-age, 2 to 20 years
- Woom: Compare woom bikes
- Islabikes: Size chart
- Trek: Precaliber kids’ bikes
- Decathlon: Btwin Original 100 20" manual
- Mercê C et al. (2022). Learning to Cycle: From Training Wheels to Balance Bike. IJERPH
- Two Wheeling Tots: Kids’ bike buying guide