Calculate your child’s body mass index to track their growth and health status. This tool helps parents and caregivers quickly assess if a child’s weight is healthy for their age and height. Use it to support everyday health planning for kids aged 2 to 19.
Child BMI Calculator
Calculate and track your child’s body mass index
BMI Result
For children aged 2-19, BMI is interpreted using age and sex-specific percentiles from CDC growth charts. Consult a pediatrician for a full health assessment.
How to Use This Tool
Follow these simple steps to calculate your child’s BMI:
- Enter your child’s age (must be between 2 and 19 years old).
- Select your child’s biological sex from the dropdown menu.
- Input your child’s height, using the unit selector to choose centimeters, inches, or feet and inches.
- Input your child’s weight, selecting kilograms or pounds as the unit.
- Click the Calculate button to view the BMI result and details.
- Use the Reset button to clear all fields and start a new calculation.
Formula and Logic
Child BMI is calculated using the same formula as adult BMI, which measures weight relative to height:
BMI = Weight (kg) / (Height (m))²
For this tool, all height and weight inputs are first converted to meters and kilograms respectively:
- Centimeters: divided by 100 to get meters
- Inches: multiplied by 0.0254 to get meters
- Feet and inches: converted to total inches first, then multiplied by 0.0254
- Pounds: multiplied by 0.453592 to get kilograms
Note that unlike adult BMI, child BMI is interpreted using age and sex-specific percentile ranges from the CDC growth charts. This tool provides the raw BMI value, which should be compared to official growth charts for accurate health assessment.
Practical Notes
Keep these lifestyle and health tips in mind when using this calculator:
- BMI is a screening tool only, not a diagnostic measure. Always consult a pediatrician for professional health assessments.
- Measure height without shoes, with the child standing straight against a wall for accuracy.
- Use a calibrated scale for weight measurements, preferably in the morning before meals.
- Child BMI percentiles vary by age and sex: a BMI considered normal for a 5-year-old may be classified differently for a 15-year-old.
- Children grow at different rates, so track BMI over time rather than relying on a single measurement.
Why This Tool Is Useful
This calculator helps parents and caregivers:
- Quickly track their child’s growth between pediatric visits.
- Understand how weight and height changes affect their child’s BMI over time.
- Make informed decisions about diet and physical activity for their family.
- Avoid manual calculation errors with automatic unit conversions.
Frequently Asked Questions
What age range is this calculator for?
This tool is designed for children and teens aged 2 to 19 years old. BMI calculations for children under 2 use different growth charts and are not supported by this tool.
Is child BMI the same as adult BMI?
The formula to calculate BMI is the same for children and adults, but the interpretation is different. Child BMI is compared to peers of the same age and sex, while adult BMI uses fixed cutoff values regardless of age or sex.
Can I use this tool for my 1-year-old child?
No, this calculator only supports children aged 2 to 19. For children under 2, consult your pediatrician who will use WHO growth charts specific to infants and toddlers.
Additional Guidance
While this tool provides a quick BMI estimate, it does not account for factors like muscle mass, bone density, or body composition. Very active children with high muscle mass may have a higher BMI that is not indicative of excess body fat. Always discuss BMI results with a healthcare provider, who can perform additional assessments if needed. For everyday health planning, pair BMI tracking with balanced nutrition and regular physical activity appropriate for your child’s age.