1. What is BMI for Children?

Body Mass Index (BMI) is a measure that uses height and weight to estimate body fat. For children and teens, BMI is age- and sex-specific and is often referred to as BMI-for-age. The NHS uses BMI percentiles to classify weight status in children.

2. How the Calculator Works

The calculator uses the standard BMI formula adjusted for age and gender:

The result is then compared to UK growth charts to determine the percentile:

• Below 5th percentile: Underweight
• 5th to 85th percentile: Healthy weight
• 85th to 95th percentile: Overweight
• Above 95th percentile: Obese

3. Understanding Percentiles

Details: Percentiles compare your child's BMI to other children of the same age and gender. A child at the 75th percentile has a higher BMI than 75% of children their age and gender.

4. Using the Calculator

Tips: Measure height without shoes and weight with minimal clothing. Use metric measurements (kg and meters) for most accurate results.

5. Frequently Asked Questions

Q1: Why is BMI different for children than adults?
A: Children's body composition changes as they grow, so BMI must be interpreted relative to other children of the same age and sex.

Q2: What if my child is above the 95th percentile?
A: Consult your GP or a pediatrician for personalized advice about healthy growth and development.

Q3: How often should I check my child's BMI?
A: NHS recommends regular checks at key stages (reception year and year 6), or annually if concerned about weight.

Q4: Are there limitations to BMI for children?
A: BMI doesn't distinguish between muscle and fat, so athletic children may have higher BMIs without excess fat.

Q5: Where can I get more information?
A: Visit the NHS website or consult your school nurse or GP for personalized advice.