Bike Sizing
Kids bike size chart
Measure your child's inseam, find the row, buy that wheel size. A 12-inch bike fits a 10–18 inch inseam, 14-inch fits 14–19, 16-inch fits 15.5–25, 20-inch fits 18.3–28. Age is a rough proxy and the brands themselves disagree about it.
| Wheel | Inseam | Height | Age brands quote | Stage |
|---|---|---|---|---|
| 12" | 10–18 in | 31–40 in | 1.5 – 3.5 | Balance bike |
| 14" | 14–19 in | 37–43 in | 3 – 5 | First pedal bike |
| 16" | 15.5–25 in | 40–47 in | 4 – 6 | First pedal bike |
| 20" | 18.3–28 in | 43–51 in | 5 – 9 | First gears |
| 24" | 26–32 in | 49–57 in | 7 – 11 | Big kid |
| 26" | 29.5–37.4 in | 55–65 in | 10 – 14 | Adult-adjacent |
Built from the inseam ranges woom, Prevelo, Guardian and Strider publish for their own bikes (read 2026-09-23). Age is the brands' figure, shown so you can see how loosely it maps.
That table is the whole page. If you only have thirty seconds: measure the inseam, find the band it lands in, buy that wheel size. Everything below explains where the numbers come from and what to do when your child lands between two rows.
Why the chart is built on inseam and not age
Wheel size does not determine whether a bike fits. Minimum saddle height does, and inseam is the measurement that decides whether your child can reach it. Two 16-inch bikes in this guide differ by more than two inches of minimum saddle height: Prevelo publishes 16.9 inches for the Alpha Two, woom publishes 19 inches for the GO 3. Same wheel, same stated age band, a child who fits one and cannot safely ride the other.
That gap is not a rounding error. It is the difference between a five-year-old planting both feet at a stop sign and a five-year-old tipping over at one.
How to read a row
Each row gives an inseam band, a height band and the age brands typically quote. Use them in that order of confidence. Inseam is a measurement, height is a decent second, and age is a marketing convenience.
If your child is between two rows
Go down, not up. A bike that is slightly small is rideable, teachable and safe. A bike that is slightly big is a bike your child will avoid for a season — which is the most expensive mistake available here, because the bike they do not ride costs the same as the one they do.
If you are shopping ahead for a gift
Measure now and buy for now. Kids grow around two to three inches of height a year at these ages, and a bike bought two sizes ahead spends a year in the garage. If you genuinely cannot measure — because it is a surprise — there is a whole page on buying a bike as a surprise that deals with guessing well.
Where these numbers came from
We did not invent this chart. Each band is the union of what woom, Prevelo, Guardian and Strider publish for their own bikes, read off their spec pages and linked below. Where they disagree, the chart takes the widest defensible span and the notes name which brand sits at each edge — because that disagreement is information you need, not noise to smooth over.
No figure on this page is an estimate. Where a manufacturer does not publish something, we say so rather than filling in the cell.
The three checks that confirm a fit
Step 01
Feet flat at the saddle's lowest setting
On a first pedal bike, your child should be able to sit on the saddle at its lowest position and put both feet flat on the ground. Not tiptoes. That is the confidence margin that keeps them riding.
Step 02
A hand's width of standover clearance
Straddling the top tube in shoes, there should be clear air between the tube and your child. This is the measurement that matters in a sudden stop.
Step 03
Brake levers they can actually squeeze
Small hands need short-reach levers. If your child has to shift their grip to brake, the bike is wrong regardless of what the size chart says. This is where brake choice stops being an abstraction.
The two age pages that this chart cannot settle on its own are the oldest ones, where 24 and 26 inch overlap: what size bike for a 9 year old and what size bike for a 10 year old.
Once you have the wheel size, fitting the bike itself is five checks and about ten minutes. They are set out in order on how to fit a kids bike.
The picks
Every figure below is the manufacturer's own published spec, linked to the page we read it from, so you can check the one number your decision turns on — here is how we choose.
Quick picks — sorted by weight
| # | Product | Score | Best for | Weight | Price |
|---|---|---|---|---|---|
| 1 |  Top pickStrider 12 Sport The widest fit range of any 12-inch balance bike we found, and the one most likely to still fit a year after you buy it. | 9.8/10 | The widest age window | 6.7 lb | |
| 2 |  woom GO 2 12.2 lb on a 14-inch wheel is the number that matters here — it is the lightest first pedal bike in this registry, and a first pedal bike is mostly a weight problem. | 9.8/10 | The lightest 14-inch | 12.2 lb | |
| 3 | 16" Prevelo Alpha Two A 16.9 in minimum saddle on a 16-inch wheel, at 12.1 lb — it bridges the gap where a child has outgrown 14-inch but can't reach a woom GO 3. | 9.7/10 | The awkward in-between size | 12.1 lb | Not sold on Amazon · Prevelo specs |
| 4 |  woom GO 4 Seven gears with a numbered indicator and 17.2 lb on the scale — the point where a kid's bike stops being a toy and starts being transport. | 9.7/10 | First gears done right | 17.2 lb |
n/p = the manufacturer does not publish that figure. Every other spec number here comes straight off their spec page. Scores are ours, on the 8.4–9.8 scale explained on our how we choose page.
Top pick — The widest age window
Category-defining · our scale
Strider 12 Sport
The widest fit range of any 12-inch balance bike we found, and the one most likely to still fit a year after you buy it.
| Wheel | 12" |
|---|---|
| Weight | 6.7 lb |
| Fits inseam | 12–18 in |
| Saddle height | 11–17 in |
| Brakes | None — riders stop with their feet |
| Gearing | None (balance bike) |
| Frame | Steel |
| Brand says | Manufacturer says 1–4 years |
Why we picked it
- 11–17 in saddle range covers a 12–18 in inseam — roughly two years of growth
- 6.7 lb, light enough for a toddler to pick up unaided
- Flat-free foam tires never need air
- Tool-free saddle and bar adjustment
Good to knowFoam tires and a steel frame mean nothing to inflate and nothing to break; there is no hand brake at this stage, so feet do the stopping.
How we checked it: Researched from published specs · Strider — 12 Sport specs
#ad · How we make money · Price as of November 12, 2026
#2 — The lightest 14-inch
Category-defining · our scale
woom GO 2
12.2 lb on a 14-inch wheel is the number that matters here — it is the lightest first pedal bike in this registry, and a first pedal bike is mostly a weight problem.
| Wheel | 14" |
|---|---|
| Weight | 12.2 lb |
| Fits inseam | 16–19.1 in |
| Saddle height | 15.5–19.3 in |
| Brakes | Two independently operated mini V-brakes; ships with a rear coaster brake as a CPSC requirement |
| Gearing | Single speed, 18t front / 10t rear |
| Frame | 6061 aluminum |
| Brand says | Manufacturer says 3–4.5 years, rider height 37–43 in |
Why we picked it
- 12.2 lb — roughly 34% of the median four-year-old's body weight
- Two real hand brakes with short-reach levers
- 15.5 in minimum saddle height suits a genuinely small first-pedaler
- Coaster brake can be removed by a shop if you want a pure freewheel
Good to knowThe coaster brake ships fitted alongside the hand brake, and the 19.3 in saddle ceiling means a tall four-year-old is ready for the GO 3.
How we checked it: Researched from published specs · woom — GO 2 specs
#ad · How we make money · Price as of November 12, 2026
#3 — The awkward in-between size
Category-defining · our scale
Prevelo Alpha Two
A 16.9 in minimum saddle on a 16-inch wheel, at 12.1 lb — it bridges the gap where a child has outgrown 14-inch but can't reach a woom GO 3.
| Wheel | 16" |
|---|---|
| Weight | 12.1 lb |
| Fits inseam | 15.5–22 in |
| Saddle height | 16.9–25.2 in |
| Brakes | Independently operated dual hand brakes, kid-sized levers |
| Gearing | Single-speed freewheel, 18t / 10t |
| Frame | Triple-butted 6061 aluminum, THRU-TUBE design |
| Brand says | Manufacturer says 4–6 years |
Why we picked it
- 16.9 in minimum saddle height — over 2 in lower than the woom GO 3
- 12.1 lb (manufacturer figure, without pedals)
- 8.3 in of saddle travel
Good to knowSingle speed, direct-sale only, and the published weight is measured without pedals fitted.
How we checked it: Researched from published specs · Prevelo — Alpha Two specs
Not sold on Amazon · Prevelo specs
#4 — First gears done right
Category-defining · our scale
woom GO 4
Seven gears with a numbered indicator and 17.2 lb on the scale — the point where a kid's bike stops being a toy and starts being transport.
| Wheel | 20" |
|---|---|
| Weight | 17.2 lb |
| Fits inseam | 22.1–27.9 in |
| Saddle height | 22.4–28.7 in |
| Brakes | Two independently operated mini V-brakes |
| Gearing | 7 speed with a child-friendly gear indicator |
| Frame | Butted 6061 aluminum |
| Brand says | Manufacturer says 6–8 years, rider height 45–51 in |
Why we picked it
- 17.2 lb with gears fitted — about 34% of the median seven-year-old
- Gear indicator makes shifting teachable
- 6.3 in of saddle adjustment
Good to knowThe 22.4 in minimum saddle rules out shorter six-year-olds, and it runs rim brakes rather than discs.
How we checked it: Researched from published specs · woom — GO 4 specs
#ad · How we make money · Price as of November 12, 2026
Questions parents actually ask
01What size bike does my child need?
Measure their inseam and match it to the chart: 10–18 in fits a 12-inch wheel, 14–19 in fits 14-inch, 15.5–25 in fits 16-inch, 18.3–28 in fits 20-inch, 26–32 in fits 24-inch. Where a child lands between two sizes, take the smaller one.
02What inch bike does my child need?
Kids bikes are sized by wheel diameter in inches, and the useful ranges overlap heavily. A 16-inch wheel covers roughly a 15.5 to 25 inch inseam depending on the model, so the brand matters as much as the number.
03How do I size a child for a bike?
Stand them against a wall in shoes, put a hardcover book spine-up between their legs with the pressure a saddle would apply, mark the top of the spine and measure from the floor. That figure is the inseam. Compare it to the minimum saddle height of the bike you are considering, not to the wheel size.
04What age is a 14 inch bike?
Manufacturers quote roughly 3 to 5 years for a 14-inch bike, but their own inseam figures range from 14 inches (Prevelo Alpha One) to 16 inches (woom GO 2) as the minimum. The age band is the least precise part of the answer.
05What size person fits a 16 inch bike?
A child with roughly a 15.5 to 25 inch inseam and a height around 40 to 47 inches. The spread is wide because minimum saddle heights vary by more than two inches between 16-inch models.
06What size person fits a 20 inch bike?
Roughly an 18.3 to 28 inch inseam, about 43 to 51 inches tall. Guardian publishes 18.3 inches as its 20 Small minimum leg length; woom's geared GO 4 wants at least 22.1 inches.
07Is a bigger bike better because they'll grow into it?
No. A bike that is too big is a bike a child avoids, and avoidance costs a whole riding season. Buy the size that fits today and sell it on when it does not.
Our recommendation
Top pick
9.8/10Strider 12 Sport
The widest age window. Foam tires and a steel frame mean nothing to inflate and nothing to break; there is no hand brake at this stage, so feet do the stopping.
#ad · How we make money · Price as of November 12, 2026
Runner-up
9.8/10woom GO 2
The lightest 14-inch. The coaster brake ships fitted alongside the hand brake, and the 19.3 in saddle ceiling means a tall four-year-old is ready for the GO 3.
#ad · How we make money · Price as of November 12, 2026
Sources
Read next
- Bike SizingHow to measure your child's inseamTwo minutes, a book and a wall. The only measurement that matters.
- Bike SizingKids bike wheel size by ageAge bands by wheel size — and how far the brands disagree.
- Bike SizingKids bike seat heightTwo correct saddle heights, and when to move between them.
- Bike SizingIs my child's bike too big?Five checks that settle it, without a tape measure.
- Bike Sizing12-inch vs 16-inch kids bikeThe saddle ranges barely overlap. Which side of the line your child is on.
- First Pedal BikesBest 18-inch kids bikesThe size the specialists skip — and what to buy either side of it.