Child BMI Calculator
BMI and category for children.
Enter your values
Enter the weight in kg.
Enter the height in cm.
Enter the age in years.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- BMI
- 16.8
- Category (approximate)
- Healthy weight
- Typical BMI for age
- 18.7
- Difference from typical
- -1.9
- Healthy weight range
- 31.8–40.4 kg
Quick answer
Children's BMI is interpreted against age and sex percentiles, not the fixed adult cut-offs.
BMI = kg ÷ m²
At a glance
| What it does | BMI and category for children. |
|---|---|
| Category | Health |
| Inputs needed | Weight, Height, Age |
| Main output | BMI |
| Formula | BMI = kg ÷ m² |
| Cost | Free — no sign-up, no download |
How to use the Child BMI Calculator
- 1Enter the child's weight in kilograms.
- 2Enter height in centimetres.
- 3Enter their age in years.
Inputs explained
- Weight(kg)
- Enter the weight in kg.
- Height(cm)
- Enter the height in cm.
- Age(years)
- Enter the age in years.
Worked example
Using the values the calculator loads with:
Inputs
- Weight32 kg
- Height138 cm
- Age10 years
Results
- BMI16.8
- Category (approximate)Healthy weight
- Typical BMI for age18.7
- Difference from typical-1.9
- Healthy weight range31.8–40.4 kg
Frequently asked questions
Why can't I use adult BMI?
Children's body composition changes with age, so cut-offs shift each year.
Is BMI accurate for athletic kids?
It can overstate fat in muscular children — use it alongside other measures.
What do I need to enter into the Child BMI Calculator?
Just 3 values: weight, height, age. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Child BMI Calculator work out the answer?
Children's BMI is interpreted against age and sex percentiles, not the fixed adult cut-offs. It applies the formula BMI = kg ÷ m² and shows the working so you can check each step by hand.
Is the Child BMI Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.