How to choose the right size kids ebike for your child

Every Zippi sale starts with the same question: "How do I know which size to get?" Fair question, and one most kids bike brands answer badly. Manufacturers love age charts because they're easy to print. Kids don't actually fit age charts. A four-year-old can be 95cm or 115cm. A six-year-old can have the inseam of an eight-year-old. Age is a guess. Here's how we actually do it.

The one measurement that matters: inseam

Inseam is the distance from the ground to the crotch when your kid is standing flat-footed. It's the single best predictor of whether a bike will fit, because it tells you whether they can comfortably plant their feet on either side of the bike.

To measure inseam at home:

1. Stand the kid against a wall, shoes off, feet flat on the floor.
2. Put a hardcover book between their legs and push it up firmly against the crotch — like a bike seat would press up.
3. Mark the top of the book on the wall.
4. Measure from that mark to the floor.

That's the inseam. Write it down in centimetres.

Why inseam beats height

You can fit a tall, long-torso, short-leg kid and a shorter, all-leg kid into the same height bracket — and they'll need different bikes. We've put 110cm-tall kids on a Rippa 16" and 110cm-tall kids on a Rippa 12" depending on their inseam. Inseam doesn't lie.

The match-up

Here's how Zippi's range matches against inseam:

Inseam	Best fit	Notes
35–45 cm	Ride 10"	First-timers, throttle balance bike. Most 2-5 year olds.
40–50 cm	Rippa 12"	Bigger than the Ride 10", still a balance bike. Most 3-6 year olds.
50–62 cm	Rippa 16"	The middle child. Pump-track ready. Most 5-10 year olds.
60–75 cm	Rippa 20"	Big-kid energy, high-speed switch. 9-15 year olds.
70–82 cm	Rebel 20" Pro	Pedal e-bike, real suspension. 10+ for trail-ready kids.
78 cm+	Rebel 24" Pro	The flagship. Teens stepping into adult-bike territory.

You'll notice the brackets overlap. That's deliberate. A kid sitting at the top of the Rippa 12" range and the bottom of the Rippa 16" range could go either way. Which brings us to the question we get every day.

Between sizes: size up or stay?

This is the question. Our answer changes based on the kid.

Size up if:

• They're already a confident rider. Bigger bike = longer rides, less risk of outgrowing it in six months.
• They're tall for their age and growing fast. You'll be in the next size by Christmas anyway.
• You'll be passing it down to a sibling. Sizing up extends the bike's useful life across two kids.

Stay smaller if:

• They're a first-timer or nervous on two wheels. A bike that's too big undermines confidence — they can't get a foot down in a wobble.
• They're going to be the only kid riding it. You'd rather they fit it perfectly for a year than awkwardly for two.
• Their inseam is at the bottom of the bigger size's range. Bottom-of-range is a warning sign.

The single biggest sizing mistake we see parents make: buying a bike too big because they don't want to buy another one in 18 months. We get the impulse — these aren't cheap toys. But a kid on an oversized bike loses confidence, rides less, and the bike sits in the garage. A perfectly-sized bike gets ridden every day. The math usually works out the same.

Height as a sanity check

If you can't measure inseam right now (their bedroom is on the other side of the house, they're at school, etc.), here's a rough height fallback:

• 85-105 cm tall: Ride 10"
• 95-115 cm tall: Rippa 12"
• 115-140 cm tall: Rippa 16"
• 135-160 cm tall: Rippa 20"
• 150-170 cm tall: Rebel 20" Pro
• 165 cm+: Rebel 24" Pro

Use height to narrow it to two candidates. Use inseam to pick between them.

The "will they grow into it" question

Yes, kids grow. Our bikes are designed with that in mind:

• Seat posts adjust 5-8 cm on every model. That's typically 12-18 months of growth on a balance bike, 18-24 months on a larger Rippa or Rebel.
• Handlebars rise with allen key tweaks on most models.
• Resale is real. A 5-year-old Zippi Ride 10" in clean condition sells for 60-70% of new on Facebook Marketplace, easily. You're not buying disposable.

So when a parent asks "will they outgrow it?" — yes, eventually. But it'll be sized correctly for the next 18 months, not the next 18 weeks, and it'll have resale value or a younger sibling waiting.

Still not sure?

Email us — sales@zippi.net.au — with your kid's inseam, height, age, and a sentence about their riding experience. We'll tell you which bike to buy. We do it every day, and we're not paid on commission — we're paid by the fact that you'll be back when your second kid is old enough.

#raisebalancedkids