20 inch wheel, height, inseam
20 Inch Bike Size Chart
Use this 20 inch bike size chart when a bike is sold by wheel diameter. A 20 inch bike for what height question usually means a kids bike or youth BMX, but adult BMX also uses 20 inch wheels, so height, inseam, saddle height, top tube length, and riding style all matter.
Data reviewed: 2026-05-18
Model geometry is a reference check; sizing comes from the available size chart rows.
Enter your measurements to see your recommended size, backup size, confidence, and why it fits.
Kids bike size chart by height
Match child height to 12, 14, 16, 20, 24, and 26 inch wheel sizes.
Bike wheel size chart
Compare wheel labels across kids, BMX, folding, mountain, road, and hybrid bikes.
Kids bike size calculator
Calculate a kids wheel-size shortlist from height, age, inseam, and confidence.
BMX bike size calculator
Check 16, 18, 20, and 24 inch BMX options by height and top tube.
Youth bike size chart
Compare 20, 24, 26 inch, and adult XS transition sizes.
Sizing notes
Read the chart, then check the bike.
20 inch usually means wheel size
For kids and BMX bikes, 20 inch describes the wheel diameter, not the frame. The actual fit depends on saddle range, standover, reach, and control.
Kids bikes need saddle and brake checks
A child in the 115-135 cm height range often starts with a 20 inch kids bike, but inseam, lowest saddle height, brake reach, and confidence decide whether it is safe.
BMX uses top tube length
A 20 inch BMX wheel can fit older kids, teens, and adults. For adult BMX, compare top tube length and cockpit feel instead of choosing by wheel diameter alone.
Compare adjacent wheel sizes
If the rider is near the edge of the 20 inch range, compare 18 inch for easier handling or 24 inch for taller youth riders who need more room.
20 inch bike for what height
Size
20 inch kids bike
Height
115-135 cm / 3'9"-4'5"
Inseam: 50-60 cm inseam
Size
20 inch youth BMX
Height
120-150 cm / 3'11"-4'11"
Inseam: Check standover and handlebar reach
Size
20 inch adult BMX
Height
150 cm+ / 4'11"+
Inseam: Use top tube length more than wheel size
Size
Compare 18 inch
Height
105-125 cm / 3'5"-4'1"
Inseam: Shorter riders or newer riders
Size
Compare 24 inch
Height
130-150 cm / 4'3"-4'11"
Inseam: Taller kids needing more rollover
FAQ
Short answers for choosing a size before purchase.
What height is a 20 inch bike for?
A 20 inch kids bike often fits riders around 115-135 cm or 3'9"-4'5", but inseam, lowest saddle height, brake reach, and confidence decide the final fit.
Is a 20 inch bike for kids or adults?
Both can be true. A 20 inch kids bike uses 20 inch wheels for child sizing, while adult BMX also commonly uses a 20 inch wheel and should be chosen by top tube length.
How do I use a 20 inch bike size chart?
First decide whether the bike is a kids bike, youth BMX, or adult BMX. Then check height, inseam, saddle range, brake reach, and top tube length where relevant.
Should I buy 20 inch or 24 inch?
Choose 20 inch when the rider needs easier control and lower standover. Compare 24 inch only when height, inseam, and reach still feel safe.