Kids Bike Size Chart: Wheel Size by Height, Age and Inside Leg

Last updated: 7 October 2026

As a rough guide to kids bike sizes, a 12-inch bike suits children about 90–105 cm tall (around 3–4 years old), a 16-inch bike suits 100–120 cm (4–6 years), a 20-inch bike suits 115–135 cm (6–9 years) and a 24-inch bike suits 125–150 cm (8–11 years). The most reliable check is your child's inside leg, compared with the bike's lowest saddle height.

We combined official sizing from Trek, Giant, woom and Frog with the specs of the Minivelo and Pony bikes we sell. Brands differ by a few centimetres, so treat the numbers as ranges and let inside leg and a test sit decide.

Kids bike size chart: what size for my child's height and age?

In short: 12-inch for about 90–105 cm, 14-inch for 95–115 cm, 16-inch for 100–120 cm, 18-inch for 115–130 cm, 20-inch for 115–135 cm, 24-inch for 125–150 cm and 26-inch for 140–165 cm.

The heights are roughly where the brands' ranges overlap. Brands usually differ by 5–10 cm: for a 20-inch bike, Trek suggests 114–132 cm while Giant suggests 120–140 cm. Age is only a guide, because children of the same age vary a lot in height, which is why Frog names its models after inside-leg length. The inside-leg column uses Frog's figures throughout so the sizes compare fairly; Frog's smallest pedal bike is 14 inches, so there is no 12-inch figure. Other brands can differ widely: Giant's 12-inch range of 36–51 cm is wider than the 36–41 cm Frog gives for its 14-inch bike, so always check saddle height as well. In Taiwan these are called "腳踏車", but the sizes work the same way.

How do I measure inside leg and saddle height?

Height narrows the choice; inside leg tells you whether your child can reach the ground. You only need a hardback book and a tape measure.

Measuring inside leg

woom's method: have your child stand straight against a wall in the shoes and trousers they will ride in, place a hardback book spine-up between their legs with the gentle pressure of a saddle, mark the top of the spine on the wall, then measure from the floor to the mark.

Comparing with saddle height

Saddle height is measured from the ground to the top of the saddle. With the saddle at its lowest, it should not be higher than your child's inside leg; for a beginner, a little lower is better so more of each foot reaches the ground. Bikes with the same wheel size can differ a lot here. In our product specifications, the Minivelo 16 has a 46–54 cm saddle height while the Pony 16 starts at 54 cm, an 8 cm difference at the lowest setting.

What we often see in store: a child who can already ride is fine with tiptoes on the ground, while a beginner needs most or all of each foot down to feel safe. Stabilisers change the picture, because the child does not need to put a foot down; once they come off, check the saddle height again.

Should I buy a size up so it lasts longer?

We would not. A bike that is too big is hard to steer and hard to stop with a foot down, and a scared child may refuse to ride. Frog's own product pages warn that buying a bike for the child to "grow into" often backfires, and woom says a smaller bike is easier to handle and less intimidating for beginners.

If your child sits in the overlap between two sizes, choose the smaller bike if they are still learning or nervous. Choose the larger bike only if they ride confidently, are near the top of the smaller size, and can still touch down on tiptoes with the saddle at its lowest. For longer use, compare the saddle adjustment range: the Minivelo 14 adjusts from 43 to 55 cm, giving 12 cm of growing room. If the favourite colour is out of stock in the right size, wait rather than size up.

How light should a kids bike be?

woom recommends that a bike weighs no more than about 35–40% of the child's body weight, and compares a heavy kids bike to an 80 kg adult learning on a 50 kg bike. We divided the weight of bikes we sell by the World Health Organization (WHO) median weight for the child's age.

The WHO medians are 16.3 kg (boys) and 16.1 kg (girls) at four, 18.3 and 18.2 kg at five, 22.9 and 22.4 kg at seven, and 28.1 and 28.2 kg at nine. For a five-year-old, the 6.2 kg Minivelo 16 is about 34% of body weight, while the roughly 9.5 kg Pony 16 is over half. The LanQ 16 figure of 8.3 kg is our own weighing with stabilisers fitted, while the others are without, so its share comes out higher. Every child is different too, so use the chart as a comparison, not a rule.

Hand brakes or a coaster brake?

Both are common. A coaster brake stops the bike when the child pedals backwards; the Trek Precaliber 12 uses one. Giant's ARX range and woom use hand brakes, as do the Minivelo 16, 20 and 24 we sell.

The international safety standard for young children's bicycles, ISO 8098:2023 (bikes with a maximum saddle height between 435 and 635 mm), requires at least two independent braking systems, one on each wheel; whether the rear one is worked by hand or foot is left to local law or custom. It also caps the grip distance between brake lever and handlebar at 75 mm, to suit small hands.

woom argues against coaster brakes: the pedals may need two to three seconds to reach a useful position, a dropped chain leaves the child with no brake, and back-pedalling too hard can lock the rear wheel. Whatever you choose, let your child try the levers to see if their fingers reach and they can pull hard enough. In Hong Kong, every bicycle must have at least one efficient braking system and a bell (Road Traffic (Construction and Maintenance of Vehicles) Regulations, regulations 87 and 88).

BMX, mountain bike or folding bike?

Think about where your child will ride and where the bike will live. In a small Hong Kong flat with a lift or stairs, weight and folded size often matter more than style.

BMX-style bikes

Simple frames and an upright position make them good for parks and cycle tracks. The Pony range we sell runs from 12 to 20 inches, and the Hong Kong distributor says it passes the EN 14765 children's bicycle test. Watch the weight: the Pony 16 is about 9.5 kg, over 3 kg more than the Minivelo 16.

Mountain bikes

From 20 inches you will find kids mountain bikes with gears and suspension, such as the Giant XTC JR 20 with a 50 mm suspension fork and 7 speeds. On flat cycle tracks, suspension adds weight and maintenance without much benefit.

Folding bikes

The Sooibe 007 Pro 14 folds to 58 × 27 × 52 cm (brand figure), small enough for a car boot or lift. The trade-off is weight: it is 7.9 kg (manufacturer figure), against 4.93 kg for the Minivelo 14. Check that the folding design does not leave the handlebar too far from the saddle for your child.

Helmets, protective gear and Hong Kong law

Your child should wear a helmet every time. Hong Kong does not yet require cyclists to wear helmets; our guide to Hong Kong's bike helmet law and choosing a helmet covers the details. Knee and elbow pads and gloves help beginners, and you can browse our helmets and protective gear.

Under section 54 of the Road Traffic Ordinance (Cap. 374), as listed by the Transport Department's Cycling Information Centre, no one may let a child under 11 ride a bicycle on a road without an adult, or hire a bicycle to a child under 11. The exception is a road or part of a road set aside for cycles where traffic signs allow children under 11 to ride alone. The penalty is a level 2 fine (HK$5,000 under Schedule 8 of the Criminal Procedure Ordinance). Cycling on a footpath without obvious necessity is also an offence (Summary Offences Ordinance, section 4(8)).

Kids bikes in stock, by size

All these bikes were in stock on 7 October 2026. Weights and height ranges are from our product pages, except the LanQ (our own weighing, 2024) and Minivelo 20 (2021 product video).

Minivelo 14: a first pedal bike light enough to push

At 4.93 kg, with a 43–55 cm saddle and short 102 mm cranks, it suits children of about 90–120 cm moving on from a balance bike. Limits: single speed, and stabilisers are sold separately.

See the Minivelo 14 in four colours, with stock

Sooibe 007 Pro 14: a folding bike for small flats

It folds to 58 × 27 × 52 cm, and the stabilisers flip up once your child can balance. Sooibe quotes 105–175 cm. Limit: at 7.9 kg (excluding stabilisers, according to retailer information) it is about 3 kg heavier than the Minivelo 14. For 16-inch wheels and gears, see the Sooibe 009 16-inch 6-speed (9.2 kg).

See the Sooibe 007 Pro colours, folded size and stock

Minivelo 16: the most common size for ages 4 to 6

At 6.2 kg it is about 34% of a five-year-old's median weight, and its 46–54 cm saddle starts 8 cm lower than the Pony 16. Limits: single speed for hilly routes, and a 54 cm maximum saddle height for fast growers.

See the Minivelo 16 in four colours, with stock

Pony 16: an affordable BMX style from 12 to 18 inches

Made in Taiwan and recommended by its Hong Kong distributor for ages 5–7 and 105–120 cm, in many colours. The same frame comes in 12, 14 and 18 inches. Limits: about 9.5 kg, roughly half a five-year-old's weight; a relatively high 54–63 cm saddle; stabilisers extra.

See the Pony 16 colours and stock

LanQ 18: a magnesium frame and disc brakes in the in-between size

A one-piece magnesium frame with mechanical disc brakes, about 8.8 kg with kickstand on our scales. The brand lists a 54–73 cm saddle and 115–145 cm riders. Limits: a little heavier than aluminium bikes such as Minivelo or Frog, and no stabilisers. More in our LanQ review.

See the LanQ 18 colours and stock

Minivelo 24 8-speed: for older children and hilly routes

A 6061 aluminium frame, fork and rims at 9.3 kg, with 8 speeds and V-brakes for riders of 125–160 cm. Limits: no suspension and no stabilisers. Under 125 cm, try the Minivelo 20 single-speed or 20-inch 8-speed.

See the Minivelo 24 8-speed colours and stock

For more brands, read our guide to eight popular kids and teen bike brands or browse all kid and youth bikes. Not sure about the size? Contact us before you buy with your child's height and inside leg.

FAQ

What height is a 16-inch bike for?

A 16-inch kids bike suits children about 100–120 cm tall, usually aged 4–6. Trek suggests 99–117 cm, Giant 105–125 cm and woom 105–120 cm, with an inside leg of about 40–53 cm (Frog 44).

What size bike for a 3-year-old?

Most three-year-olds start on a 12-inch bike, moving to 14 inches at around 95 cm tall. Trek sizes its 12-inch for ages 3–4 and 91–102 cm; woom sizes its 14-inch for ages 3–4.5 and 95–110 cm.

What height is a 20-inch bike for?

A 20-inch kids bike suits children about 115–135 cm tall, usually aged 6–9. Trek suggests 114–132 cm and Giant 120–140 cm.

What age is a 14-inch bike for?

A 14-inch bike usually suits children aged 3–5 and 95–115 cm tall. woom suggests 3–4.5 years and Pony 4–6 years, with an inside leg of roughly 36–41 cm (Frog 40).

What height is an 18-inch bike for?

An 18-inch bike suits children about 115–130 cm tall, usually aged 5–8, bridging 16 and 20 inches. Frog's 18-inch Frog 47 suits an inside leg of 43–59 cm.

Further reading

• Eight popular kids and teen bike brands
• Bike helmet law in Hong Kong and how to choose a helmet
• Eight tips for teaching a child to ride (in Chinese)
• Balance bikes: benefits and set-up (in Chinese)

Update log: 7 October 2026, rewritten in full with a size chart combining six brands, a bike-weight chart using WHO data, how to measure inside leg and saddle height, ISO 8098 brake requirements, Hong Kong law on children under 11, in-stock bikes and an FAQ. An unverified survey figure was removed.

Sources

• Giant: ARX 16, ARX 20, ARX 24, ARX 26, Animator 12
• woom: What Size is Right?; woom model pages such as woom GO 3 (age, height, weight)
• woom: bike weight; woom: coaster brakes
• Trek Precaliber 12, 16, 20 and 24 sizing (Trek product copy via dealers such as Bicycle Habitat, Cycles UK and Wheel & Sprocket)
• Frog Bikes product pages, archived: Frog 40, Frog 44, Frog 47, Frog 53, Frog 61 (frogbikes.com now redirects to Evans Cycles); Cycle Sprog: Frog 67
• WHO Child Growth Standards: weight-for-age; WHO weight-for-age, 5–10 years
• ISO 8098:2023 Cycles – Safety requirements for bicycles for young children (preview)
• Transport Department Cycling Information Centre: Road Traffic Ordinance, Cap. 374
• Hong Kong Police: cycling offence warning; CLIC: offences related to cycling
• Jollymap product pages for Minivelo, Sooibe, Pony, LanQ and Frog bikes (read 7 October 2026)