The correct bike size for your child depends primarily on their inseam. While wheel and frame size matter, choosing a bike based on inseam ensures the best fit from the start and provides room for growth, so your child can comfortably ride the bike for a year or two.
Unfortunately, most kids bike size charts focus on height and wheel size, often leaving out inseam measurements. To complicate things, size recommendations vary between brands—one chart might suggest a 16″ bike, while another recommends a 20″ for the same child. These inconsistencies make it difficult to find a perfect fit using charts alone.
So, what’s the solution? It lies in measuring your child’s inseam and matching it to the bike’s seat height. This combination offers the most accurate way to ensure a proper bike fit, even if your child can’t test the bike in person.
Why trust us? With over 15 years of experience reviewing kids’ bikes, we’ve helped hundreds of families find the perfect fit across a wide range of brands. We’ve seen firsthand the positive impact a properly sized bike can have on a child’s riding ability, from boosting confidence to improving overall control and safety.
How to Size a Child for a Bike Using Inseam
To guide you through measuring your child’s inseam and understanding why it matters, we’ve created a 6-minute video tutorial. For those who prefer reading, we’ve detailed everything you need to know in this article.
STEP 1: Measure Your Child’s Inseam
To get started, measure your child’s inseam while they wear the shoes they’re likely to use for biking. Have them stand against a wall with their back and heels flush to it. Slide a hardbound book between their legs, raising it until the spine presses firmly against their crotch.
Make sure the book is level with the floor, then measure from the ground up to the top of the book’s spine, or mark the spot on the wall where it touches. This measurement is your child’s inseam, and it will be the key to finding the perfect bike fit.
STEP 2: Narrow Down Wheel Size Based on Inseam
Using your child’s inseam measurement, use the bike size chart below to identify one or two possible wheel sizes. For example, a child with a 19″ inseam might fit both a 16″ and a 20″ bike.
| Wheel Size | Age | Inseam | Height |
| 12″ | 2 to 3 | 15 – 18″ | 36 – 39″ |
| 14″ | 2 to 4 | 15 – 20″ | 37 – 44″ |
| 16″ | 4 to 6 | 16 – 22″ | 41 – 48″ |
| 20″ | 5 to 8 | 19 – 25″ | 45 – 54″ |
| 24″ | 8 to 11 | 23 – 28″ | 49 – 59″ |
| 26″ | 10 + | 25″ + | 56″ + |
To fine-tune the fit even further, we next need to take your child’s riding experience into consideration. Their level of riding experience, helps us determine their ideal seat height range. Knowing the precise seat height range allows you to confidently assess whether a bike will truly fit your child—without needing them to try it out in person.
STEP 3: Find the Perfect Seat Height (Using Child’s Inseam and Riding Ability)
Your child’s riding ability determines how high the bike’s seat should be in relation to their inseam. The more experienced they are, the higher the seat can be positioned in relation to thier inseam.
Proper Bike Seat Height in Relation to Inseam
- Balance Bike Riders: Seat height should be 0.5″ to 1.5″ below inseam.
- Pedal Bike Riders using Training Wheels: Seat height should be equal to or up to 3″ above inseam.
- First-time Pedal Bike Riders: Set the seat height equal to their inseam for stability.
- Experienced Pedal Bike Riders: Seat height can be 2″ to 4″ above inseam for better pedaling efficiency.
By applying this range to your child’s inseam (measured in Step 1), you can calculate their ideal seat height for a new bike. For instance, a child with a 16″ inseam using training wheels would need a seat height between 16″ and 19”. However, if the same child is an experienced rider without training wheels, the seat should be raised higher, to around 18″ to 20″, for better pedaling efficiency.
| Inseam | Rider | Seat Offset | Ideal Seat Height |
|---|---|---|---|
| 13″ | Balance Bike | – 0.5″ to 1.5″ | 11.5″ to 12.5″ |
| 16″ | Training Wheels | + 0″ to 3″ | 16″ to 19″ |
| 16″ | 1st Pedal Bike | Equal | 16″ |
| 16″ | Experienced | + 2″ to 4″ | 18″ to 20″ |
STEP 4: Find the Perfect Size Bike
With your child’s ideal seat height range in hand, you’re ready to find a bike that fits. To maximize growth potential, look for bikes where the minimum seat height is close to (but not exceeding) your child’s ideal seat height.
| Inseam | Ideal Seat Height | Bike | Bike’s Seat Height |
|---|---|---|---|
| 13″ | 11.5” to 12.5” | Retrospec Cub Plus | 11.5” – 15” |
| 16″ | 16” to 19” | Biky 14 | 15.5” – 21” |
| 16″ | 16” | woom 2 | 16” – 19.1” |
| 16″ | 18” to 20” | Guardian 16 | 18.25” – 22.6” |
Where do I find the seat height of a bike?
Most kid-specific bike brands, like Woom, Prevelo, and Guardian, include seat height information in their product listings. At Two Wheeling Tots, we also provide seat height measurements in all our bike reviews and “Best of” pages, which cover the top bike options for every age and size.
Since seat height ranges vary between different wheel sizes, be sure to consider bikes in multiple wheel sizes. This flexibility helps you find the best fit and maximize the bike’s usability as your child grows.
Two Wheeling Tots Favorite Bikes by Size
- Balance Bikes – Age 1 to 3
- 12 and 14 Inch Bikes – Age 2 to 4
- 16 Inch Bikes – Age 4 to 5
- 20 Inch Bikes – Age 6 to 7
- 24 Inch Bikes – Age 8 to 10
- 26 and 27.5 Inch Bikes – Tweens
What Does a Properly Fitting Kids Bike Look Like?
Got lost in the numbers? Here’s an example of what a properly fitting bike looks for a child in each bike riding stage.
Balance Bike Riders
The seat of a balance bike should be set 0.5 – 1.5” below the child’s inseam. While seated on the bike with their feet flat on the ground, a child’s knees should be slightly bent (in an athletic stance). The slight knee bend allow them to efficiently run on the bike.
Bike with Training Wheels
The seat of a bike with training wheels should be set 0 – 3” above the child’s inseam. Kids should be able to touch the ground with their tip toes while sitting on the seat. For timid kids, touching with their feet flat is often preferred.
Kids usually stop the bike with the brakes, but they also need to able able to stop with their feet, especially while learning.
1st Pedal Bike (After a Balance Bike or Training Wheels)
The seat of a child’s first pedal bike should be set at the same height as the child’s inseam. While learning to pedal a bike, a child’s entire foot should be able to touch the ground while seated on the bike. This allows them to easily stop and start the bike without falling off. Once they gain confidence, the seat can be raised for better leg extension and pedaling efficiency.
Experienced Riders
The seat of a confident pedaler can be set 2 – 4” above their inseam. Kids should be able to touch the ground with only their tip toes. Setting the seat higher allows for proper leg extension for maximum pedaling efficiency.
Other Kids Biking Resources
Guardian Bikes RideSizer: Enter in your child age and height and Guardian’s proprietary tool will tell you which size bike is best for them.
woom Bikes Size Finder: Take out all of the guess work of buying the right size woom bike with their bike finder tool.
For additional information on child bike sizes and what other features you should look for when shopping for a bike, check out our article Best Kids Bikes: The Authoritative Buying Guide.
For young kids that have never ridden a bike, a balance bike is likely a better option for them. Check out Why a Balance Bike Should be the First Bike for Your Toddler.
