Short answer
A 20-inch wheel bike generally suits children around 5 to 9 years old, most often around 6 to 8, depending on height and inseam. Age is only a rough guide, because children of the same age vary a lot in size. Height and inseam give a better match, and brands label their sizes slightly differently.
Kids bike wheel size chart
| Wheel size | Typical age (rough) | Approximate height | Approximate inseam |
|---|---|---|---|
| 12 inch | 2 to 4 | about 2’10” to 3’4” | about 14” to 17” |
| 14 inch | 3 to 5 | about 3’3” to 3’8” | about 16” to 19” |
| 16 inch | 4 to 6 | about 3’7” to 4’0” | about 18” to 21” |
| 20 inch | 5 to 9 | about 3’10” to 4’5” and sometimes taller | about 20” to 25” |
| 24 inch | 8 to 12 | about 4’5” to 5’0” | about 24” to 28” |
Treat these as overlapping ranges. A tall six-year-old and a small eight-year-old can both be right for a 20-inch bike. For the same ranges arranged by height alone, see bike wheel sizes by rider height.
Why height and inseam beat age
Wheel size sets the overall size of a kids’ bike, and the frame is built around it. What matters for safety and confidence is whether the child can reach the ground and control the bike. That depends on inseam and height more than on birthday. A child should be able to sit on the saddle and touch the ground with the balls of their feet, ideally with a slight bend in the knees at the pedal’s lowest point, and stand over the top tube.
How to measure your child
- Measure height barefoot against a wall.
- Measure inseam from the floor up to the crotch, with a book held snugly between the legs.
- Compare both numbers to the brand’s own chart.
- If possible, have the child sit on the bike and check they can reach the grips and brake levers comfortably.
The 20-inch bike in detail
A 20-inch bike is often the first size where training wheels are no longer common, and where multi-speed gears and hand brakes begin to appear, though details vary by model. Some 20-inch bikes are lighter than others, which matters a lot for a smaller child. If your child is toward the bottom of the age or height range, a lighter model or a 16-inch bike may be easier to handle.
What about a 5-year-old?
Many 5-year-olds ride a 16-inch bike, and some taller ones are ready for 20 inch. Pick by height and inseam, not just age. If the child cannot comfortably reach the ground on a 20-inch bike, a 16-inch bike is the better choice.
Signs a bike is too big or too small
- Too big: the child cannot touch the ground, struggles to steer or stop, or leans heavily to reach the handlebars.
- Too small: knees come high toward the handlebars, the child looks cramped, or the saddle and bars are at their limits.
Avoid buying a much bigger bike for the child to “grow into.” It tends to be harder to control and can put them off riding.
Moving up to 24 and 26 inch
Around 8 to 12 years old, many children move up to 24-inch wheels, and some move straight to 26-inch bikes with an extra-small frame. Older kids and teens who are tall for their age may look at 26-inch wheel bikes or small-framed 27.5-inch bikes. A 27.5-inch bike is typically a bike for teens and adults, not for young children. The bike wheel size chart lists all of these sizes together.
FAQ
What size kid would a 20 inch bike be appropriate for?
Children roughly 3’10” to 4’5” tall, and often about 5 to 9 years old, with an inseam in the low-to-mid 20s of inches.
What bike size should I get for my height as an adult?
Adults usually choose by frame size first. See bike wheel sizes by rider height.
What age is a 27.5 inch bike for?
Usually teens and adults rather than children. Some tall older kids ride them, depending on frame size.
How do I check what size my child’s current bike is?
Read the tire sidewall or follow our guide to measuring your bike wheel size.