Children's BMI Calculator
Track your child's growth and development with our paediatric BMI calculator. Get accurate results and understand what they mean for your child's health.
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Calculate Your Child's BMI
2 years
12 years
18 years
cm
kg
BMI Results
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BMI
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Underweight
Normal
Overweight
Obese
What this means:
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BMI Percentile
Your child's BMI percentile helps compare their growth with other children of the same age and gender.
Understanding Children's BMI
BMI (Body Mass Index) is a measurement that helps assess whether your child is at a healthy weight for their age, gender, and height.
For children and teens, BMI is calculated the same way as for adults, but the results are interpreted differently. Children's BMI is compared to others in the same age and gender group using percentile charts.
BMI Categories for Children:
Underweight: Less than 5th percentile
Healthy Weight: 5th to 84th percentile
Overweight: 85th to 94th percentile
Obese: 95th percentile or higher
BMI Categories for Children and Adolescents
Based on the BMI-for-age percentile, children are classified into the following categories:
Underweight
Below 5th percentile — The child's weight is lower than expected for their age and height. This may indicate nutritional deficiencies, underlying health conditions, or simply a naturally lean build that should still be monitored.
Healthy Weight
5th to 84th percentile — The child is within a healthy weight range. This is the ideal category and indicates balanced growth. Continue maintaining a nutritious diet and active lifestyle.
Overweight
85th to 94th percentile — The child is carrying more weight than is typical for their age and height. This is a signal to review dietary habits and physical activity levels, and to consult a paediatrician for guidance.
Obese
95th percentile or above — The child's weight is significantly above the expected range. This increases the risk of developing type 2 diabetes, high blood pressure, joint problems, and psychological issues. Medical guidance is strongly recommended.
What Is BMI?
BMI, or Body Mass Index, is a simple numerical value calculated from a person's weight and height. It is one of the most widely used screening tools in healthcare to assess whether an individual falls within a healthy weight range. The formula divides weight in kilograms by the square of height in metres (kg/m²), producing a single number that can be compared against standard reference charts.
While BMI was originally developed for adults, it is equally important for children and adolescents — though it is interpreted differently. In children, BMI is age- and gender-specific, and results are expressed as percentiles rather than fixed categories. This is because a child's body composition changes significantly as they grow.
How Is Children's BMI Calculated?
The formula for BMI is straightforward:
BMI = Weight (kg) ÷ Height² (m²)
For example, a child weighing 30 kg with a height of 1.3 m would have a BMI of 30 ÷ (1.3 × 1.3) = 17.8
When Should You Consult a Paediatrician?
While our BMI calculator is a helpful starting point, it is important to seek professional guidance if:
Your child's BMI consistently falls outside the healthy range
There has been a sudden or unexplained change in your child's weight
Your child has a poor appetite, low energy, or frequent fatigue
You are concerned about your child's eating habits or body image
There is a family history of obesity, diabetes, or cardiovascular conditions
Your child's growth appears to have stalled or accelerated unexpectedly
At Motherhood Children's Hospital, our paediatric specialists can perform comprehensive growth assessments and provide personalised guidance tailored to your child's unique needs.
Tips for a Healthy Child
1
Balanced Nutrition
Ensure your child eats a variety of fruits, vegetables, whole grains, and lean proteins.
2
Regular Physical Activity
Children should get at least 60 minutes of physical activity each day.
3
Adequate Sleep
Ensure 9-12 hours of sleep per night for school-aged children.
4
Regular Check-ups
Schedule routine paediatric visits to monitor growth and development.
Concerned About Your Child's Health?
Our paediatric specialists are here to help. Schedule a consultation to discuss your child's growth and development.