1. What is BMI to Percentile Conversion?

The BMI to percentile conversion calculates a child's BMI relative to others of the same age and sex using z-scores and CDC/WHO growth charts. It provides a more accurate assessment of weight status in children than BMI alone.

2. How Does the Calculator Work?

The calculator uses the z-score formula:

Where:

• \( BMI \) — Body Mass Index (kg/m²)
• \( M \) — Median BMI value for specific age and sex
• \( S \) — Standard deviation value for specific age and sex
• \( Z \) — Z-score (standard deviations from the mean)

Explanation: The z-score is converted to a percentile using the standard normal distribution, showing where the child's BMI falls compared to peers.

3. Importance of BMI Percentile

Details: BMI percentile is the standard measure for assessing weight status in children aged 2-20 years. It helps identify underweight, healthy weight, overweight, and obesity categories.

4. Using the Calculator

Tips: Enter the child's BMI along with the appropriate M and S values from CDC/WHO growth charts for their exact age and sex. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Where do I find M and S values?
A: These values come from CDC or WHO growth reference tables, specific to the child's exact age in months and sex.

Q2: What do the percentiles mean?
A: Below 5th = underweight; 5th-85th = healthy weight; 85th-95th = overweight; Above 95th = obese.

Q3: Why use percentiles instead of BMI categories?
A: Children's body composition changes with growth, so percentiles account for normal developmental changes.

Q4: How accurate is this calculation?
A: The calculation is accurate when using the correct M and S values for the child's exact age and sex.

Q5: Can this be used for adults?
A: No, BMI percentiles are only appropriate for children aged 2-20. Adults use standard BMI categories.