Your Kid's Bike Sizing Guide
I've sold hundreds of kids bikes since opening my bike shop, and I have a group of goto testers (about 15 kids that try out all the things before I sell it). I have tried different styles of bikes for sizing and I have a goto method of helping you figure out what size bike is right for your kid.
If you ask me my why, it's my kids. That is why there is a bike shop and why I am so motivated to help people bike more often. Bike Shop Girl was one of the first bike shops to partner with kid's bike brands woom and Prevelo after experiencing first hand what a quality kid's bike can do. As our silent partner (my wife) is a pediatrician, we have a lot of thoughts about proper bike fit and why a quality bike is so crucial for many kids to learn how to ride safely at a younger age.
Things to Look for In a Quality Kid's Bike
1. Weight is THE biggest factor for a kid's bike. I have personally picked up a Specialized 16" kids bike and it weighed 25 pounds. This is a bike designed for a 4-5 year old and my 4-year-old barely weighed 32 pounds. Can you imagine riding a bike that weighs 78% of your body weight?!
2. Say no to training wheels and bikes designed for them. Starting your kid off with a balance bike like a Woom 1 or Strider allows them to learn how to balance and glide. When they are ready to transition to a pedal bike simply take the pedals off the next size bike. If they are starting at an older age, take the pedals off the bike that fits them! I do not recommend bikes that are designed for training wheels because they are significantly higher off the ground and don't make it easy for kids to touch the ground when sitting on the seat.
3. Hand brakes only. Buy a bike with handbrakes and no coaster brakes! If you are buying a bike from a quality kid's bike manufacturer like woom, Prevelo or Cleary they will only have hand brakes for the bigger sizes. Some of the smaller models are legally required to have coaster brakes and the brands sell an after market freewheel option. Buy that option! Why? It is REALLY difficult for balance bike kids to be used to their feet being available for balance and now having to use them to stop. Additionally, when we transition from balance bike to pedal bike the very first thing we do is teach kids how to brake with their hands. This is often done by taking off the pedals of the new bike so they can focus on the size of the new bike and stopping properly.
How to Properly Size a Kid's Bike
Now that we discussed the 3 things to look for in a kid's bike, we now need to figure out which size bike you need. The two questions I ask are, what is your kid's inseam with shoes on AND how confident is your child on their balance bike or in life. More on those two things below.
Measuring for a kid's inseam:
I recommend standing the child against a wall with shoes on, place a book between their legs and measure to the top of the book. This inseam gives you a sense of what standover and seat height you'll need.
The most important part is standover so your kid has room when they step off the seat. When they are on the seat they will be pointing their toes which gives them 1-2" of additional height.
What's their confidence like?
There are two things I really suggest against for getting your kids biking, the first is pushing them when they aren't interested. My daughter rode a scooter for a long time. That was fine! She was moving her body and loved exploring. Once her friends started biking faster than she could scooter then she became interested. The second is buying a bike they can grow into. This may be fine for bigger kids with good bike handling, but it could really upset a kid's confidence or potentially injure them.
Example: My daughter is a skilled cyclist. At 4.5 she was ready to try something for gears so we tried the Cannondale Quick 20". She was BARELY able to touch when on the seat with both feet. When she was on uneven terrain or stopping suddenly she would fall over. Due to this we switched her to the smallest fitting 20" kid's bike I know of, the Prevelo Alpha 3. The seat was able to go down significantly and she was much safer and more confident on the bike.
It is hard to think about buying a bike they may outgrow in a year but if it means they are biking more in that year than a bike too big I personally think it is worth it. All of the bikes Bike Shop Girl sells are premium kid's bike and you will get a good percentage of your original purchase price back when you sell it. The Woom bikes for example NEVER go on sale so people are really excited when they get 20% off. It is worth noting that the 14 & 16" bikes have the shortest life span due to child growth during those years BUT it is amazing that we are getting kids to bike when they are 3, 4, 5 years old!
One Last Thing
Not all bikes are created equal from quality to sizing. A kid that fits a 16" Woom bike may be able to fit on a 20" Prevelo bike. Look for stand over height, WEIGHT, and purpose of bike in that order to figure out what is best for your own unique child. I'm working on a shared google spreadsheet to share all of the numbers from bikes I have tried, spreadsheet can be found here.
Kid's Bike Stand Over & Seat Height List (Work in progress)
Woom 1 (balance bike)
Strider (balance bike)
Woom 2 (14" Pedal Bike)
Prevelo Alpha 1 (14" Pedal Bike)
Woom 3 (16" Pedal Bike)
Prevelo Alpha 2 (16" Pedal Bike)
Woom 4 (20" Pedal Bike)
Prevelo Alpha 3 (20" Pedal Bike)
Cleary Owl (20" Pedal Bike)
Cannondale Quick 20" (20" Pedal Bike)
Woom 5 (24" Pedal Bike)
Cleary Meerkat (24" Pedal Bike)
Cannondale Quick 24" (24" Pedal Bike)
Cannondale Trail 24" (24" Pedal Bike)