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A bike gives kids freedom, fitness and fun — wherever their pedals take them. At Giant, we’ve designed our kids’ bike range to suit riders of all ages and abilities, combining lightweight design, durability and easy handling.

Our bikes are built to grow with your child, covering ages 4 – 11+ with the ARX (lightweight) and STP (mountain).

Use this guide to find the right size for your young rider — and remember, you can buy online or Click & Collect in-store, so your child’s new bike is safely built and ready to ride.

Why Bike Size Matters

Getting the right size is essential for safety, control and confidence.

A bike that’s too big or too small can affect balance and make riding uncomfortable.
Our guide below provides age-based recommendations, but every child grows differently — so if you’re unsure, visit your local Giant retailer for tailored advice.

ARX Kids Bikes

Lightweight and Super Easy to Ride

Our ARX range is built to be among the lightest in its class, making it easier for kids to ride, steer and stop with confidence.

ARX 16” | Age 4-6 Years
ARX 16” | Age 4-6 Years
Light, agile and easy to handle. The ARX 16 helps young riders build confidence with a lightweight aluminium frame and versatile tyres ready for paths, parks and gentle trails.

Shop ARX 16

ARX 20inch
ARX 20” | Age 6-9 Years
Stepping up from single-speed to 8-speed gearing, the ARX 20 gives growing riders more range to explore hills and varied terrain. Still lightweight, still fun — just built for bigger adventures.

Shop ARX 20

ARX 24 Inch
ARX 24” | Age 9–11 years
With 24-inch wheels, an 8-speed drivetrain and low bottom bracket for improved stability, the ARX 24 keeps things light and confidence-inspiring for developing riders.

Shop ARX 24

ARX 26 Inch
ARX 26” | Age 11+ years
The biggest in the ARX family, with youth-specific handlebars for smaller hands and a comfort-focused Giant Selle Royal Vivo Jr saddle with an 8 speed drivetrain — perfect for longer rides.

Shop ARX 26

Giant STP Youth Bikes

Built for Off-Road Fun

For kids ready to hit the trails, our STP range introduces off-road riding in a safe, controlled way. Each model includes a lightweight aluminium frame, suspension fork, and trail-ready tyres for grip and confidence.

STP 20 Inch
STP 20” | Age 6–9 years
The first step into mountain biking. A 60mm front suspension fork smooths out bumps and the durable 20-inch wheels are ideal for learning basic off-road skills.

Shop STP 20

STP 24 Inch
STP 24” | Age 9–11 years
Built for progression. The STP 24 features an 80mm suspension fork, wider 2.2” tyres and powerful disc brakes for extra control as kids test their trail skills.

Shop STP 24

STP 26 Inch
STP 26” | Age 11+ years
Ready for more challenging terrain. The STP 26 includes a 100mm Crest suspension fork with remote lockout and modern trail geometry for agile, confident handling.

Shop STP 26

Buying Online for Christmas?

Many parents purchase kids bikes online as Christmas gifts.  Our size guide gives you everything you need to buy confidently from home.

Tips for buying online:

  • Use the age and wheel size guide above as your starting point.
  • If your child is near the top of the age range, consider sizing up.
  • All ARX and STP bikes include adjustable seat and handlebar positions, giving plenty of room to grow.
  • Add a Hoot or Path ARX kids’ helmet for a perfect match in colour and safety.
  • Choose Click & Collect at checkout to have your new bike professionally assembled by your nearest Giant retailer.

Kids Bike Helmets — Safety First

While helmets aren’t mandatory, they’re essential for safety and peace of mind.
The Hoot ARX and Path ARX helmets are lightweight, well-ventilated and secure — designed specifically for smaller heads and maximum comfort.


Available in seven colours, they’re the perfect match for any Giant kids bike.
Starting at £39.99, they’re a smart investment in every ride.
Shop Kids Helmets

Shop Kids Helmets

Find Your Perfect Fit

Every child is unique, and while this guide provides a great starting point, a professional fit check can make all the difference.

Bike size is based on wheel diameter, not frame size. Use our ARX kids’ bike size chart or visit a Giant retailer for a personalised fitting.

To measure your child's inseam, have them stand with their back against a wall, wearing only socks. Place a large hardcover book (spine facing up) between their legs, pushing it gently up to mimic a bike saddle. Mark where the book spine meets the wall, then measure from the mark down to the floor. This measurement directly correlates to the bike's standover height.

No, it is not recommended. A bike that is too large or too heavy will be difficult to handle, raise the center of gravity, and make it harder for the child to stop safely or put their feet flat on the ground. A correctly sized bike is crucial for building confidence and ensuring safety.

The average age for a child to ride without training wheels is typically 4 to 7 years old, but it varies widely. Children who use a balance bike first often achieve this milestone earlier, sometimes as young as 3 or 4, because they've already developed the necessary core balance skills.

Bike weight is one of the most important factors. An ideal kids' bike should weigh no more than 30-40% of the child's body weight. Lighter bikes (often featuring aluminum frames) are easier for a child to control, maneuver, accelerate, and stop, which directly improves confidence and enjoyment.