Bicycles come in sizes. Not just wheel sizes. When most people see sizing, they think of the wheel size. This is how bikes are sold at department stores. Those frames are sized generically. BMX sizing also differs from road or mountain bike sizing. BMX sizing is done with the top tube (TT). The top tube is the uppermost tube of the frame. A difference of half-an-inch may not sound like much, but it really is. To measure the top tube, measure from the center of the seat tube to the center of the head tube.
BMX race bikes come in these general sizes: Micro, Mini, Junior, Expert, Expert XL, Pro, Pro XL, Pro XXL. On older race bikes you may encounter Mini XL and Junior XL. Longer sizes such as Pro XXXL do exist, but these are manufacturer specific. It is important to size a race bike correctly. Too long and it handles like a dump truck. Too short and it is unstable. Ultimately, racing a bike you are most comfortable with is the best advice we can give. Find what works for you. The 20” wheel size race bikes are called ‘class’ bikes; 24” wheel size race bikes are ‘cruisers.’ Cruiser sizing for adults is more or less two sizes, and kid cruiser sizes exist, but are becoming rare and niche these days, and are found most often at the National level races.
Try out the rental bikes at your local track. They should have multiple sizes for available. Up until rider’s hit the Pro size frames they’ll likely have to size up every two seasons. The below sizes are just guidelines. We can help you pick the right size.
Race bike sizing (the ages are a general age range):
Micro: 15 to 16.5” TT. This typically has an 18” wheel (a few may have 20”) and is for 4- to 5-year-olds.
Mini: 17 to 17.5” TT This is usually the first pedal bike for most riders. Ages 5 to 7.
Junior: 17.25 to 18.75” TT From about ages 7 to 10.
Expert: 19 to 19.5” TT Ages 10-13.
Expert XL: 19.5 to 20” TT This size is good for ages 10 to 13. This is an in-between size. The Expert XL is unique since it often uses a blend of pro size parts and expert size parts. It has also been called a 'short pro.'
Pro: 20.25 to 20.5” TT Ages 12 and up.
Pro XL: 20.75 to 21.25” TT Ages 12 and up, height from 5’7” to 6’0”. Most adult riders find this to be their preferred size due to increased stability without much reduction in maneuverability. For many adults coming into 20" class racing the Pro XL is a good starting point.
Pro XXL: 21.25 to 22” TT Height from 6’0” and up. Riders under 6’ might like the XXL because it is very stable for them.