A 6-year-old needs a 16-inch bike if they're shorter than about 3 ft 11 in (120 cm), and a 20" if they're taller and already pedal confidently. The average height at this age is about 3 ft 10 in (116 cm), but it ranges from 3 ft 6 in to 4 ft 1 in (106-125 cm).
- Typical height
- 3′10″ 116 cm; range 3′6″–4′1″ (106–125 cm)
- Their bike
- 16" or 20-inch
- Bike weight
- < 13.4 lb 6.1 kg: 30% of about 45 lb (20 kg)
Calculate with their exact height
How tall is a 6-year-old?
According to the World Health Organization (WHO), half of 6-year-old boys are taller than 45.7 in (116.0 cm) and half of girls are taller than 45.3 in (115.1 cm). Between the 3rd and 97th percentiles (94% of kids) the range is wide: from 3′6″ to 4′1″ (106-125 cm). In the US, the CDC growth charts give a median of 45.4 in (115.4 cm) for boys and 45.2 in (114.7 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 | 42.0 in (106.7 cm) | 45.7 in (116.0 cm) | 49.3 in (125.2 cm) |
| Girls | 41.5 in (105.5 cm) | 45.3 in (115.1 cm) | 49.1 in (124.8 cm) |
What size bike they need
Kids vary a lot at this age: there's almost 8 in (20 cm) between the 3rd and 97th percentiles. 16" bikes go up to 3 ft 10 in-3 ft 11 in (117-120 cm), and 20" bikes start at 3 ft 9 in-3 ft 11 in (114-120 cm) depending on the brand (Trek from 114 cm, Woom from 115 cm, Decathlon from 120 cm). If your child is in that range, let the inseam decide: the seat on Woom's 20" bike doesn't go below 22.4 in (56.8 cm). If they can't reach the ground with their toes, stick with the 16" for another year.
| Size | Height | Inseam |
|---|---|---|
| 16-inch | 3′4″–3′11″ (102–120 cm) | 17–22 in (44–55 cm) |
| 20-inch | 3′9″–4′5″ (115–135 cm) | 20–24 in (50–62 cm) |
How to check the fit
On a 20": seated, the toes touch the ground and, with the pedal at the bottom, the leg is almost straight. It's the first size where the seat is set "like on a grown-up bike." On a 16", if the seatpost is already maxed out and their knees come up above their hips when pedaling, they've outgrown it.
Ideal bike weight
At 6, a child weighs about 44 lb (20 kg): the ideal bike, 13 lb (6 kg) or less. That's easy at 16" (light ones weigh 12-13 lb / 5.5-6 kg) and hard at 20": Woom's 20" weighs 17.2 lb (7.8 kg) without pedals, and steel ones top 22 lb (10 kg). If you're torn between the two sizes, weight is another argument for the 16" for smaller kids.
Brakes: coaster brake or hand brakes
From this age on, two hand brakes. Decathlon's 20" bikes have V-brakes front and rear; Woom's 20" bikes have V-brakes or hydraulic discs depending on the version. Teach them to use both brakes together and not to lock the front wheel in a turn.
Gears
Not needed on a 16". On a 20" they show up for the first time: there are single-speed versions (Btwin Original 100) and 7-speed ones (Woom GO 4). If you live somewhere flat, a single speed is fine; if there are hills, a few gears with a twist shifter are easy to understand.
Training wheels or a balance bike
The vast majority of 6-year-olds already ride without training wheels. If yours still uses them, take them off now: at this age, with the remove-the-pedals-and-lower-the-seat method, they usually learn in a few afternoons. A bike that fits and doesn't scare them speeds things up a lot.
What to look for when you buy
- Measure: under 3 ft 9 in (115 cm), 16"; over 3 ft 11 in (120 cm), 20"; in between, the inseam decides.
- On a 20", look at the weight before the number of gears.
- Two hand brakes with adjustable-reach levers.
- 1.75-2 in tires if they'll ride on trails.
- Check the seatpost's minimum insertion mark with the seat at their height.
Frequently asked questions
16 or 20 inch bike for a 6-year-old?
16" if they're shorter than 3 ft 9 in-3 ft 11 in (115-120 cm) or still lack confidence; 20" if they're taller than 3 ft 11 in (120 cm) and can touch the ground with their toes.
What age is a 20-inch bike for?
For kids from 3 ft 9 in to 4 ft 5 in (115-135 cm) tall, which is usually ages 6 to 9.
Does a bike for a 6-year-old need gears?
It isn't essential. On a 20" they help if there are hills, but they add weight; on a 16" they aren't needed.
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