The short answer
- Age 4 to 7: a 50cc mini. Seat height around 21 to 24 inches.
- Age 8 to 10: still a 50cc for most kids, especially if it's their first bike. A taller or more experienced rider around 9 or 10 is ready for a 60cc.
- Age 11 to 13: a 60cc or a 110cc, or an electric if they are close to adult height.
- Teen, 5 ft and up: an adult-sized bike. Our Sykerun X5 electric fits riders from about 4 ft to 5 ft 11 in.
But age is genuinely the worst variable to size a bike by. A small 9-year-old and a tall 6-year-old can need the same bike. Size by inseam, not birthday.
The two-foot test
Sit them on the bike, on level ground, in the boots they'll actually ride in.
- Both feet flat, knees clearly bent. The bike is too small. They'll be cramped and they will outgrow it in a season, though for a genuinely nervous first-timer this is not the worst place to start.
- Balls of both feet down, heels slightly up. This is the target. They can hold the bike up at a stop and they still have room to grow into it.
- One toe down at a time, tipping to reach. Too big. They cannot catch the bike when it leans, and a bike they can't catch is a bike that lands on them.
- Feet dangling. Far too big. Don't.
Everything else is secondary to this. A confident rider on a bike that fits progresses faster than a scared rider on a bike they've been told to grow into.
Sizing chart
| Age | Typical inseam | Seat height to look for | Engine |
|---|---|---|---|
| 4 to 5 | 16 to 19 in | 19 to 22 in | 50cc |
| 6 to 7 | 19 to 22 in | 21 to 25 in | 50cc |
| 8 to 9 | 22 to 25 in | 24 to 28 in | 50cc to 60cc |
| 10 to 11 | 25 to 27 in | 26 to 30 in | 60cc to 110cc |
| 12 to 13 | 27 to 30 in | 28 to 32 in | 110cc and up, or electric |
| 14+ | 30 in and up | 32 in and up | adult-sized |
How to measure inseam: stand them against a wall in socks, put a book between their legs pulled up snug, mark the top of the book, measure to the floor.
Age by age
What size dirt bike for a 6-year-old?
A 50cc, essentially without exception. At this age the priorities are a low seat, light weight so they can pick it up themselves, and an adjustable speed limiter so you can cap the speed at a jog while they learn. Engine size is close to irrelevant compared to those three things.
Start with the limiter almost fully closed and open it a quarter turn at a time as their control improves.
What size dirt bike for an 8-year-old?
Still a 50cc for a first bike. An 8-year-old with two seasons of riding behind them and a 25 inch inseam might be ready to move up, but if this is their first bike, a 50cc with the limiter opened part way is exactly right.
A common mistake here is buying up a size because they seem confident. Confidence on a pedal bike does not transfer to a machine that accelerates on its own.
What size dirt bike for a 10-year-old?
This is the split. A first-time 10-year-old is fine on a 50cc and will not be bored, because the limiter can be opened to about 32 mph, which is plenty fast on dirt. A 10-year-old who has ridden for a few years and is at the top of the height range is ready to move up.
That is where our 60cc double exhaust at $380 sits. It is the same chassis as the 50cc with a bigger engine and a 220 lb rider limit, running about 35 mph wide open, and it still has the adjustable limiter. For a rider around 9 and up who has outgrown the 50cc but is nowhere near adult size, it is the natural next bike.
If you're not sure, the 50cc is the safer purchase and holds its value well if they do move up.
Teens and adults
Once a rider is past about 4 ft 10 in, a 50cc mini stops making sense. They'll be folded onto it and it won't pull their weight.
This is where our electrics come in. The Sykerun X5 at $975 fits riders from roughly 4 ft to 5 ft 11 in, carries up to 265 lbs, and has three gears so you can lock a new rider in first at about 15 mph and open it up later. The Sykerun X7 at $1,350 is the adult bike, fitting 4 ft 8 in to 6 ft 3 in and carrying up to 330 lbs.
Before you buy either one, read our Sykeruns X5 review. It publishes the real world range, which is well under the number on the box, and the same goes for the X7.
Weight limits matter too
Height gets all the attention but weight capacity is a real limit. Our 50cc is rated to 170 lbs and the 60cc to 220 lbs. Past that the suspension is fully compressed all the time, the bike handles badly, and parts wear fast. The X5 is rated to 265 lbs and the X7 to 330 lbs.
Questions
Should I buy a size up so they grow into it?
No. This is the most common and most expensive mistake in this whole category. A rider who cannot get their feet down cannot hold the bike up at a stop, which means dropping it, which means fear, which means they stop wanting to ride. Buy what fits now. Mini bikes resell easily.
Is 50cc too slow for a 10-year-old?
Not with the limiter open. Wide open it runs about 32 mph, which on dirt is genuinely fast. Most kids are limited by skill long before they're limited by the bike.
What is the difference between the 50cc and the 60cc?
The engine size and the double exhaust. Everything else is the same bike. The 60cc runs about 35 mph instead of 32 and takes a 220 lb rider instead of 170, which makes it the right pick for a bigger kid who is not yet adult sized.
My kid is tall for their age. Can they skip to a bigger bike?
Fit it by the two-foot test, not the birthday. If a tall 7-year-old fits a bigger bike properly and rides with control, that's fine. Size and skill are separate things though, so keep the speed capped either way.
How long will they fit a 50cc?
Typically several years, because the limiter lets the bike's speed grow with the rider even though its size doesn't. A lot of families get from age 5 to age 11 out of one bike.
Once the size is settled, our buying guide walks through the rest of the choice, gas against electric included.
Not sure what fits your rider? Text their age, height and weight to 623 320 8984 and we'll tell you straight, including telling you to buy the cheaper bike when that's the right answer.
Plugged by 50CC is an independent retailer. We do not manufacture, assemble, modify or service the bikes we sell. Every bike ships sealed in its factory crate exactly as it reaches us, about 90% assembled from the factory, and final assembly and setup are completed by the buyer. Off-road use only. Riders under 18 should always be supervised by an adult.
Everyone should wear a helmet and protective gear.