BMI Calculator: Check Your Body Mass Index
BMI (Body Mass Index) is a screening measure of weight relative to height, calculated as weight in kilograms divided by height in meters squared (kg/m²). This calculator computes your BMI in metric or imperial units and shows your WHO weight category and the healthy weight range for your height.
BMI Calculator: Check Your Body Mass Index
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Formula: BMI = weight (kg) / height (m)^2
Worked example — BMI: 24.3 - Normal Weight | Health Risk: Low
Medical disclaimer: This calculator is provided for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Results are general estimates and may not reflect your individual circumstances. Always consult a qualified healthcare professional before making decisions about your health.
Reviewed for accuracy by Daniel Agrici, Founder & Lead Developer · Editorial policy
How is BMI calculated?
BMI = weight (kg) / height (m)^2
BMI compares body weight with height. In metric units, divide weight in kilograms by height in meters squared. In imperial units, use BMI = [weight in lbs x 703] / [height in inches]^2.
How do you calculate BMI step by step?
Example 1: Normal BMI Calculation
Problem:Calculate BMI for a 35-year-old male who is 5'10" (178 cm) and weighs 170 lbs (77 kg).
Solution:Height in meters = 178 / 100 = 1.78 m Weight in kg = 170 x 0.4536 = 77.1 kg BMI = 77.1 / (1.78)^2 = 24.3 Category: Normal Weight Ideal weight range: about 129 to 173 lbs
Result:BMI: 24.3 - Normal Weight | Health Risk: Low
Example 2: Obese BMI Calculation
Problem:Calculate BMI for a 45-year-old female who is 5'4" (163 cm) and weighs 200 lbs (91 kg).
Solution:Height in meters = 163 / 100 = 1.63 m Weight in kg = 200 x 0.4536 = 90.7 kg BMI = 90.7 / (1.63)^2 = 34.1 Category: Obese Class I (30-34.9) Ideal weight range: about 107 to 144 lbs Weight to lose for normal BMI: about 56 lbs
Result:BMI: 34.1 - Obese Class I | Increased risk of type 2 diabetes and cardiovascular disease
Example 3: Underweight BMI Calculation
Problem:Calculate BMI for a 22-year-old female who is 5'7" (170 cm) and weighs 105 lbs (48 kg).
Solution:Height in meters = 170 / 100 = 1.70 m Weight in kg = 105 x 0.4536 = 47.6 kg BMI = 47.6 / (1.70)^2 = 16.5 Category: Severe Thinness (below 16) Ideal weight range: about 121 to 163 lbs Weight to gain for normal BMI: about 16 lbs
Result:BMI: 16.5 - Severe Thinness | Health Risk: Very High
What else do people ask about BMI?
What is BMI and what does it measure?
BMI, or Body Mass Index, is a screening tool that compares weight and height. It is useful for broad health screening, but it does not directly measure body fat.
What is a healthy BMI range?
For most adults, a BMI from 18.5 to 24.9 is considered a healthy range. Lower values indicate underweight status, while higher values move into overweight and obesity ranges.
What are the limitations of BMI?
BMI does not separate fat from muscle, does not show where body fat is stored, and does not fully account for age, sex, ethnicity, or athletic build. It works best alongside other health measures.
How do I estimate my ideal weight?
A common BMI-based estimate uses the normal BMI range of 18.5 to 24.9 and multiplies those values by your height in meters squared. That gives a practical healthy-weight range for your height.
Is BMI accurate for children?
Adult BMI ranges are not used for children and teens. Younger users need age- and sex-specific BMI percentile charts, which is why child and teen BMI tools are handled separately.
What is body composition and why is it better than BMI alone?
Body composition describes what your body is actually made of: skeletal muscle, fat mass, bone mineral density, and water. Unlike BMI — which divides weight by height squared and cannot distinguish a pound of muscle from a pound of fat — body composition identifies whether weight is metabolically active tissue or stored energy. Healthy body fat percentages vary by sex and age: for women, 20-32% is generally considered healthy; for men, 8-19%. Measurement methods include DEXA scans (most accurate, ±1-2%), hydrostatic weighing, Bod Pod air displacement, bioelectrical impedance (consumer scales, ±3-5%), and skinfold calipers. A muscular person with a BMI of 27 (overweight) might have excellent body composition, while a sedentary person with a normal BMI could have metabolically risky visceral fat levels.
Is BMI an accurate measure of health?
BMI (Body Mass Index = weight in kg ÷ height in m²) is a quick, free screening tool with clear population-level correlations to health risk — the overweight range (25-29.9) and obese range (30+) are associated with higher rates of type 2 diabetes, cardiovascular disease, and joint problems. However, BMI has well-documented limitations. It cannot distinguish muscle from fat: a 200 lb athlete with 10% body fat and a 200 lb sedentary person with 35% body fat have identical BMIs but vastly different health profiles. It also ignores fat distribution — visceral fat around abdominal organs (measured by waist circumference) is far more metabolically dangerous than subcutaneous fat. Additionally, BMI thresholds were derived from European populations and may be less accurate for Asian, Black, and other ethnic groups. For a fuller picture, combine BMI with waist circumference, body fat percentage, and blood panel results.
References
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