BMI Calculatorv1.0.0

Use this BMI Calculator to estimate Body Mass Index for adults and BMI percentiles for children and teens. Enter height, weight, age, and sex, then select your preferred units. View a clear BMI value, category, and, when applicable, a percentile based on standard growth references.

• Select US or Metric units to reveal the matching height and weight fields.
• Choose an Age Input Method. Enter years and months, or provide a date of birth with a measurement date.
• Pick Sex to enable percentile calculations for ages 2 to 19 years.
• Enter Height and Weight in the visible fields.
• Calculate to see BMI, category, and, for ages 2 to 19 years, a percentile.

• Calculate Adult BMI for ages 20 years and older using the standard formula for US or Metric units.
• Calculate Child and Teen BMI for ages 2 to 19 years, then estimate a percentile using age- and sex-specific LMS parameters.
• Assign a Weight Category based on adult cutoffs or pediatric percentiles.
• Persist Inputs and Settings in your browser so you can return without re-entering values.

• Enter ages for children and teens as exact years and months, or use date of birth for greater precision.
• Enter adult ages as 20+ if you prefer a quick adult calculation.
• Use whole numbers or decimals for height and weight. The calculator formats large numbers for readability.
• Switch units at any time to compare results in US and Metric measurements.

• Adult example: Select US units. Enter 5 feet 6 inches and 150 pounds. Enter age as 20+. Click Calculate to see BMI and the adult category.
• Child example: Select Metric units. Enter 140 cm and 38 kg. Enter age as 10 years 0 months and select the correct sex. Click Calculate to see BMI, percentile, and pediatric category.

Body Mass Index (BMI) is a screening tool used to estimate body fat based on a person's height and weight. It helps identify potential weight categories such as underweight, healthy weight, overweight, or obese. This calculator provides BMI values and categories for adults aged 20 and older, and for children and teens aged 2 to 19, it also generates BMI percentiles and categories based on age and sex. For younger individuals, BMI is plotted on a growth chart to help interpret the results in the context of normal development.

Please note that small differences in rounding of age, height, or weight may cause results to vary slightly between calculators. BMI is only one potential indicator of health and should not be used alone to assess an individual's well-being. Additional factors, such as personal medical history, lifestyle habits, physical examination findings, and laboratory tests; should also be considered. It is important to consult with a healthcare provider to interpret BMI in the context of overall health. This tool is for informational purposes only and is not a substitute for professional medical advice or diagnosis.

This BMI calculator can be used in a variety of situations to support general health awareness and monitoring. Below are common use cases for both adults and children:

• General health screening: Quickly assess whether an individual is underweight, at a healthy weight, overweight, or obese.
• Pediatric growth tracking: Monitor BMI percentiles in children and teens to evaluate growth patterns over time.
• Fitness planning: Support weight management goals by establishing a baseline BMI and tracking progress.
• Clinical support: Use as a supplemental tool in health consultations to discuss body composition and associated health risks.
• Educational purposes: Teach individuals and families how height, weight, age, and sex impact BMI and health status.

Body Mass Index (BMI) is a widely used tool for assessing weight categories, but it has important limitations that can lead to inaccurate or misleading results. BMI is calculated using only height and weight, which means it does not measure body fat directly. As a result, it cannot distinguish between fat, muscle, bone, or water weight. This can be misleading for individuals with high muscle mass, such as athletes, who may be classified as overweight or obese despite having low levels of body fat.

BMI also ignores where fat is distributed in the body. Fat stored around the abdomen poses a greater health risk than fat in other areas, but BMI cannot capture this detail. In addition, BMI does not account for age, sex, or ethnic differences. For example, older adults may have a normal BMI but still carry excess body fat due to muscle loss. Some ethnic groups may also face higher health risks at lower BMI levels, making general BMI cutoffs less accurate for everyone.

• Individuals with high muscle mass or athletic builds
• Older adults with reduced muscle mass
• People from ethnic groups with different health risk thresholds
• Pregnant individuals
• People with medical conditions affecting weight or body composition

While BMI can be a useful screening tool, it should not be used as the only measure of health. Additional methods such as waist circumference, body fat percentage, and clinical evaluation provide a more complete picture of an individual's health status.

For adults (20 years and older):

US Units: BMI = (weight in pounds / height in inches^2) × 703

Metric Units: BMI = weight in kilograms / height in meters^2

Categories: <18.5 (Underweight), 18.5-24.9 (Healthy), 25-29.9 (Overweight), ≥30 (Obese)

Use Case: Enter height and weight for an adult (e.g., "20+" years) to get BMI and category.

For children/teens (2-19 years):

1. Calculate BMI as above.

2. Use LMS method: Z = [(BMI / M)^L - 1] / (L × S)

Where L (power), M (median), S (coefficient of variation) are age- and sex-specific parameters.

3. Convert Z-score to percentile using an approximation of the normal distribution.

Categories: <5% (Underweight), 5-85% (Healthy), 85-95% (Overweight), ≥95% (Obese)

Use Case: Enter age (e.g., 10 years), height, weight, and sex to get BMI, percentile, and category.

This tool is intended for informational and educational purposes only. It does not provide medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for any health-related concerns or decisions.