1. What is the BMI to Percentile Conversion?

The BMI to percentile conversion uses z-scores based on CDC/WHO growth charts to determine how a child's BMI compares to others of the same age and sex. This 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 for specific age and sex
• \( S \) — Standard deviation for specific age and sex

Explanation: The z-score indicates how many standard deviations a child's BMI is from the reference population mean for their age and sex.

3. Importance of BMI Percentile

Details: BMI percentile is the preferred measure for assessing weight status in children and adolescents (ages 2-20) as it accounts for normal growth patterns and variations by age and sex.

4. Using the Calculator

Tips: Enter the child's BMI along with the appropriate M (median) and S (standard deviation) values from CDC/WHO growth charts for their specific age and sex.

5. Frequently Asked Questions (FAQ)

Q1: Where can I find M and S values?
A: These values are available in CDC growth charts or WHO growth standards for specific ages and sexes.

Q2: How do I interpret the z-score?
A: Positive z-scores indicate BMI above the median, negative below. Percentiles can be derived from standard z-score tables.

Q3: What are the BMI percentile categories?
A: Underweight (<5th), Healthy weight (5th-85th), Overweight (85th-95th), Obese (≥95th percentile).

Q4: Why use z-scores instead of direct percentiles?
A: Z-scores provide more precise measurement at extremes of the distribution (very high or very low BMI values).

Q5: Is this calculator suitable for adults?
A: No, BMI percentiles are only meaningful for children and adolescents. For adults, use standard BMI categories.