Cdc Bmi Percentile Calculator For Children

CDC BMI Percentile Equation:

\[ Z = \begin{cases} \frac{(BMI / M)^L - 1}{L \times S} & \text{if } L \neq 0 \\ \frac{\ln(BMI / M)}{S} & \text{if } L = 0 \end{cases} \] \[ \text{Percentile} = 100 \times \Phi(Z) \]

BMI Percentile:

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the CDC BMI Percentile Calculator?

The CDC BMI Percentile Calculator estimates a child's BMI percentile using the LMS method from CDC growth charts. This percentile indicates how a child's BMI compares to others of the same age and gender.

2. How Does the Calculator Work?

The calculator uses the CDC LMS method:

\[ Z = \begin{cases} \frac{(BMI / M)^L - 1}{L \times S} & \text{if } L \neq 0 \\ \frac{\ln(BMI / M)}{S} & \text{if } L = 0 \end{cases} \] \[ \text{Percentile} = 100 \times \Phi(Z) \]

Where:

\( BMI \) — Body Mass Index (kg/m²)
\( M \) — Median BMI for age and gender
\( L \) — Box-Cox power for age and gender
\( S \) — Coefficient of variation for age and gender
\( Z \) — Standard deviation score
\( \Phi \) — Standard normal cumulative distribution

Explanation: The LMS method accounts for the skewed distribution of BMI in children by using age- and gender-specific L, M, and S values.

3. Importance of BMI Percentile

Details: BMI percentile is the preferred measure for assessing weight status in children aged 2-20, as it accounts for normal growth patterns and gender differences.

4. Using the Calculator

Tips: Enter BMI in kg/m² and age in years (2-20). For accurate results, use exact age (including decimal for months) and measured height/weight.

5. Frequently Asked Questions (FAQ)

Q1: What do the percentile results mean?
A: Below 5th = underweight; 5th-85th = healthy weight; 85th-95th = overweight; 95th+ = obese.

Q2: Why use percentiles instead of BMI categories?
A: Children's body composition changes with growth, so percentiles account for normal developmental changes.

Q3: Where do the L, M, S values come from?
A: These are derived from CDC growth charts based on national survey data.

Q4: Is this calculator for adults?
A: No, this is for children 2-20 years. Adults use standard BMI categories (18.5-24.9 = normal).

Q5: How often should BMI be checked in children?
A: The AAP recommends annual BMI screening from age 2, with more frequent monitoring if concerns arise.