Child Height Reference
One table connecting a child’s height to a starting-point bike wheel size and car-seat stage, drawn from the same functions behind the Car Seat & Bike Size Finder and the Child Growth Percentile Calculator.
Read this before the tables below.
Car seats:every stage shown here is a general starting point, not a rule. Your car seat’s own printed height and weight limits, and the car-seat law in your area, are the actual authority — both vary by seat and by jurisdiction, and both change over time. This page gives no installation instructions; if you’re unsure your seat is installed correctly, a certified Child Passenger Safety Technician can check it in person.
Growth percentiles:a percentile is a position in a range of typical heights for an age, not an assessment, a target, or a grade. A healthy child can sit anywhere in that range. Anything you’re concerned about belongs in a conversation with your pediatrician, who can see your child’s full history — this page cannot.
Height → bike wheel size → car-seat stage (starting point)
Every row comes from the same findCarSeatAndBike() logic the calculator above uses — nothing here is a separate, hand-typed table.
| Height | Bike wheel | Car-seat stage (starting point) |
|---|---|---|
| 70 cm (28″) | 12″ | Rear-facing car seat |
| 75 cm (30″) | 12″ | Rear-facing car seat |
| 80 cm (31″) | 12″ | Rear-facing car seat |
| 85 cm (33″) | 12″ | Rear-facing car seat |
| 90 cm (35″) | 12″ | Forward-facing harness |
| 95 cm (37″) | 12″ | Forward-facing harness |
| 100 cm (39″) | 14″ | Forward-facing harness |
| 105 cm (41″) | 14″ | Booster seat |
| 110 cm (43″) | 16″ | Booster seat |
| 115 cm (45″) | 16″ | Booster seat |
| 120 cm (47″) | 20″ | Booster seat |
| 125 cm (49″) | 20″ | Booster seat |
| 130 cm (51″) | 20″ | Booster seat |
| 135 cm (53″) | 24″ | Booster seat |
| 140 cm (55″) | 24″ | Booster seat |
| 145 cm (57″) | 26″ | Adult seat belt |
| 150 cm (59″) | 26″ | Adult seat belt |
“Starting point” means exactly that: check it against your own seat’s label before you rely on it for anything.
Typical height range by age (boys)
The 10th, 50th, 90th-percentile heights the growth calculator’s own reference data and normal-distribution model produce for each age, plus the bike/car-seat starting point at the middle (50th-percentile) height.
| Age | 10th percentile | 50th percentile | 90th percentile | At the middle height → |
|---|---|---|---|---|
| 2 | 82 cm | 87 cm | 92 cm | 12″ bike, rear-facing car seat |
| 3 | 90.5 cm | 96 cm | 101.5 cm | 12″ bike, forward-facing harness |
| 4 | 97.1 cm | 103 cm | 108.9 cm | 14″ bike, forward-facing harness |
| 5 | 103.7 cm | 110 cm | 116.3 cm | 16″ bike, booster seat |
| 6 | 109.3 cm | 116 cm | 122.7 cm | 16″ bike, booster seat |
| 7 | 115 cm | 122 cm | 129 cm | 20″ bike, booster seat |
| 8 | 120.6 cm | 128 cm | 135.4 cm | 20″ bike, booster seat |
| 9 | 125.3 cm | 133 cm | 140.7 cm | 20″ bike, booster seat |
| 10 | 130 cm | 138 cm | 146 cm | 24″ bike, booster seat |
| 11 | 134.7 cm | 143 cm | 151.3 cm | 24″ bike, booster seat |
| 12 | 140.4 cm | 149 cm | 157.6 cm | 26″ bike, adult seat belt |
Typical height range by age (girls)
| Age | 10th percentile | 50th percentile | 90th percentile | At the middle height → |
|---|---|---|---|---|
| 2 | 81 cm | 86 cm | 91 cm | 12″ bike, rear-facing car seat |
| 3 | 89.5 cm | 95 cm | 100.5 cm | 12″ bike, forward-facing harness |
| 4 | 96.1 cm | 102 cm | 107.9 cm | 14″ bike, forward-facing harness |
| 5 | 102.7 cm | 109 cm | 115.3 cm | 14″ bike, booster seat |
| 6 | 108.4 cm | 115 cm | 121.6 cm | 16″ bike, booster seat |
| 7 | 114 cm | 121 cm | 128 cm | 20″ bike, booster seat |
| 8 | 119.7 cm | 127 cm | 134.3 cm | 20″ bike, booster seat |
| 9 | 125.3 cm | 133 cm | 140.7 cm | 20″ bike, booster seat |
| 10 | 130 cm | 138 cm | 146 cm | 24″ bike, booster seat |
| 11 | 135.7 cm | 144 cm | 152.3 cm | 24″ bike, booster seat |
| 12 | 142.3 cm | 151 cm | 159.7 cm | 26″ bike, adult seat belt |
How to read the two tables together
The top table answers “my child is this tall — what starting point should I check against?” The age tables answer a different question: “is this height typical for this age?” They are deliberately kept separate, because collapsing them into one number invites exactly the mistake this page is trying to avoid — treating a single figure as a verdict. A child at the 10th-percentile height for their age is not behind, and a child at the 90th is not ahead of anything. They are simply two children on different parts of the same normal range.
Notice, too, how much the percentile columns spread out by age — roughly 10 centimetres between the 10th and 90th percentile at age 2, widening to nearly 20 centimetres by age 12. That widening is real and expected. It is also why an age-based rule of thumb for bike size or car-seat stage gets less reliable as kids get older: the range of “normal” sizes at any given age keeps growing, while your child is always exactly one specific height.
Frequently Asked Questions
Does this table replace my car seat's manual or my local law?
No — nothing here does. The car-seat stage in this table is a general starting point only. Your specific seat's printed height and weight limits, and the car-seat law where you live, always govern. Both have changed repeatedly over the years and vary by seat and by jurisdiction, which is exactly why we don't print a single age or height as "the" cutoff.
Does this table install my car seat for me?
No, and we don't provide installation steps anywhere on this site. Correct installation is the single most commonly failed part of car-seat safety, and it depends on your specific seat and vehicle in ways a general page can't safely cover. If you have any doubt about your installation, a certified Child Passenger Safety Technician can check it in person, often for free, and that's always the better call than a website.
What does the growth-percentile part of this table actually show?
It shows a spread of typical heights for a given age and sex — the height a shorter-than-average, an average, and a taller-than-average child of that age tends to be. It is not a target, a grade, or a health assessment. A real child's own pediatrician tracks their individual growth curve over time, which this reference cannot do.
Why does the same height map to a different bike size than the same age?
Kids of the same age vary a lot in height, and a bike sized purely by age can be badly wrong for a child who is shorter or taller than typical. This table is built primarily from height for that reason — see the worked comparison in the sizing-a-bike-by-height guide linked below.
General reference only, not medical, safety, or installation guidance. Always follow your car seat’s own manual and label, your local car-seat law, and your pediatrician’s assessment of your own child.
Use it with
- Car Seat & Bike Size Finder— get a single answer for your own child’s exact age and height.
- Child Growth Percentile Calculator— check your own child’s height or weight against the reference data behind the age tables above.
- What a Growth Percentile Does — and Doesn’t — Tell You — why a single number is a position, not a verdict.
- Car-Seat Stages Explained: Why the Manual Always Wins — the reasoning behind the starting-point stages above.
- Sizing a Kid’s Bike by Height, Not Age — a worked example of how far an age-only guess can miss.