BMI Calculator for Men, Women, Kids & Teens by Age and Gender Online!

Advanced BMI Calculator

Accurate BMI calculation for Men, Women, Children & Teens with age-specific percentiles

Calculate Your BMI

Metric (kg/cm)

Imperial (lb/in)

Male

Female

For accurate results, ages 2-120

BMI Charts by Age & Gender

Children (2-19 years) - CDC Growth Charts

BMI-for-age percentiles

Based on CDC growth charts

For children & teens, BMI is age and gender-specific. Percentiles indicate how a child's BMI compares to others of the same age and gender.

Adults (20+ years) - WHO Classification

Standard BMI categories

Same for all adults

For adults, BMI categories are consistent regardless of age or gender, though health risks may vary.

BMI Interpretation by Age & Gender

For Men

Men typically have more muscle mass and less body fat than women at the same BMI. A BMI of 22-25 is often considered ideal for men.

Health risks: Men with high BMI face increased risks of heart disease, hypertension, and type 2 diabetes.

For Women

Women naturally have higher body fat percentages. A BMI of 18.5-24.9 is healthy, but women may store fat differently (pear vs apple shape).

Health risks: Women with high BMI have increased risks of gestational diabetes, PCOS, and certain cancers.

For Children (2-12)

Children's BMI is plotted on growth charts to determine percentiles. Categories: Underweight (<5th), Healthy (5th-85th), Overweight (85th-95th), Obese (≥95th).

Note: Rapid growth periods can affect BMI readings.

For Teens (13-19)

Teen BMI accounts for puberty changes. Percentiles are gender-specific. Healthy weight is 5th-85th percentile for age and gender.

Note: Teen athletes may have higher BMI due to muscle mass.

Underweight

Adults: BMI < 18.5

Children/Teens: < 5th percentile

May indicate malnutrition, eating disorders, or other health issues.

Normal/Healthy Weight

Adults: BMI 18.5 - 24.9

Children/Teens: 5th - 85th percentile

Associated with lowest health risks for most people.

Overweight

Adults: BMI 25 - 29.9

Children/Teens: 85th - 95th percentile

Increased risk of developing health problems.

Obesity

Adults: BMI ≥ 30

Children/Teens: ≥ 95th percentile

High risk of serious health conditions.

Important Limitations: BMI does not distinguish between muscle and fat. Athletes may have high BMI due to muscle mass. Older adults may have normal BMI but high body fat (sarcopenic obesity). Always consult healthcare professionals for personalized health assessment.

This calculator uses CDC growth charts for children/teens (2-19) and WHO classification for adults (20+). Percentiles are estimated based on standardized growth data.

How BMI is Calculated

BMI Calculation Formula

Body Mass Index (BMI) is calculated using the following mathematical formula:

For Metric System (kg/cm):

BMI = weight (kg) ÷ height² (m²)

Where height in meters = height in cm ÷ 100

For Imperial System (lb/in):

BMI = (weight (lb) ÷ height² (in²)) × 703

The 703 factor converts lb/in² to kg/m²

Step-by-Step Calculation Example

Let's calculate BMI for a person who weighs 70 kg and is 175 cm tall:

  1. Step 1: Convert height to meters: 175 cm ÷ 100 = 1.75 m
  2. Step 2: Square the height: 1.75 × 1.75 = 3.0625 m²
  3. Step 3: Divide weight by height squared: 70 ÷ 3.0625 = 22.86
  4. Step 4: The BMI is 22.9 (rounded to one decimal)

BMI Categories and Interpretation

For Adults (20+ years):

BMI Range Category Health Risk
Below 18.5 Underweight Possible malnutrition, osteoporosis
18.5 - 24.9 Normal/Healthy Weight Lowest health risk
25 - 29.9 Overweight Moderate health risk
30 - 34.9 Obesity Class I High health risk
35 - 39.9 Obesity Class II Very high health risk
40 and above Obesity Class III Extremely high health risk

For Children & Teens (2-19 years):

For children and teens, BMI is interpreted differently using percentiles:

  • Underweight: BMI less than the 5th percentile for age and gender
  • Healthy Weight: BMI from 5th to less than 85th percentile
  • Overweight: BMI from 85th to less than 95th percentile
  • Obese: BMI at or above 95th percentile

Understanding Percentiles for Children

A percentile shows how a child's BMI compares to other children of the same age and gender:

Example: 10-year-old boy with BMI at 75th percentile

This means:

  • His BMI is greater than 75% of 10-year-old boys
  • His BMI is less than 25% of 10-year-old boys
  • He is in the healthy weight category (between 5th and 85th percentile)

Special Considerations by Age Group

Children (2-12 years):

  • BMI changes significantly with age and growth patterns
  • Uses CDC growth charts for accurate assessment
  • Regular monitoring is more important than a single measurement
  • Growth spurts can temporarily affect BMI

Teens (13-19 years):

  • Puberty affects body composition significantly
  • Muscle development in boys can increase BMI without indicating fat
  • Girls naturally develop higher body fat percentages
  • Teen athletes may have misleading BMI readings

Adults (20+ years):

  • Standard BMI categories apply to all adults
  • Muscle mass differences between genders affect interpretation
  • Older adults may have "normal" BMI but high body fat (sarcopenic obesity)
  • Pregnancy affects BMI calculation in women

Limitations of BMI

While BMI is a useful screening tool, it has important limitations:

BMI Does NOT Account For:

  • Muscle Mass: Athletes may have high BMI due to muscle, not fat
  • Bone Density: Individuals with heavier bones
  • Body Fat Distribution: Where fat is stored (apple vs pear shape)
  • Ethnic Differences: Some ethnic groups have different body compositions
  • Age-Related Changes: Muscle loss in older adults
  • Pregnancy Status: BMI is not accurate during pregnancy

Alternative Measurements

For more accurate health assessment, consider these additional measurements:

1. Waist-to-Hip Ratio (WHR)

Formula: WHR = waist circumference ÷ hip circumference

  • Better indicator of abdominal fat
  • Healthy: Men < 0.90, Women < 0.85

2. Waist Circumference

  • High risk: Men > 102 cm (40 in), Women > 88 cm (35 in)
  • Direct measure of abdominal fat

3. Body Fat Percentage

  • Healthy range: Men 8-19%, Women 21-33%
  • Requires special equipment (calipers, BIA scales, DEXA)

Health Recommendations by BMI Category

If Your BMI Indicates Underweight:

  • Consult with a healthcare provider to rule out medical causes
  • Focus on nutrient-dense foods to gain healthy weight
  • Consider strength training to build muscle mass
  • Monitor for signs of eating disorders

If Your BMI Indicates Healthy Weight:

  • Maintain current healthy habits
  • Continue regular physical activity (150+ minutes/week)
  • Eat a balanced diet with plenty of fruits and vegetables
  • Monitor weight regularly to catch any changes early

If Your BMI Indicates Overweight or Obesity:

  • Consult with a healthcare provider for personalized advice
  • Aim for gradual weight loss (0.5-1 kg per week)
  • Increase physical activity gradually
  • Focus on sustainable lifestyle changes, not quick fixes
  • Consider working with a registered dietitian

Medical Disclaimer

Important: This BMI calculator provides estimates based on mathematical formulas. It is NOT a diagnostic tool. BMI is a screening measure that does not account for individual variations in body composition. Always consult with a qualified healthcare professional for personalized health assessment and advice. This information should not replace professional medical guidance.