BMI Calculator Online — Body Mass Index Calculation Using WHO Formula
Professional free body mass index calculator for quick assessment of weight-to-height ratio. Calculation according to international WHO standards with detailed result analysis and personalized recommendations.
What is Body Mass Index and Why Calculate It
Body Mass Index (BMI) is a medical indicator that allows assessing the correspondence of a person's mass to their height. Developed by Belgian mathematician Adolphe Quetelet in the 19th century, today BMI is the main tool for diagnosing obesity and underweight.
BMI calculation formula: weight (kg) ÷ height² (m). For example, with weight 70 kg and height 170 cm: BMI = 70 ÷ (1.7)² = 24.2.
BMI significance for health: weight control, prevention of cardiovascular diseases, type 2 diabetes, arthritis and other diseases related to excess weight.
BMI Classification According to World Health Organization Standards
Underweight (BMI < 18.5): may indicate malnutrition, chronic diseases or genetic predisposition. Risks include osteoporosis, anemia, decreased immunity.
Normal weight (BMI 18.5-24.9): optimal weight-to-height ratio. Lowest risk of developing chronic diseases related to weight.
Overweight (BMI 25.0-29.9): moderate excess weight that requires attention. Increased risk of developing diabetes, hypertension, gallstone disease.
Class I obesity (BMI 30.0-34.9): significant excess weight requiring medical attention and lifestyle correction.
Class II obesity (BMI 35.0-39.9): severe obesity with high risk of complications.
Class III obesity (BMI ≥ 40.0): morbid obesity requiring urgent medical intervention.
Features of BMI Calculation for Different Population Groups
For children and adolescents: percentile tables are used that take into account age and gender. Adult BMI is not applied to children under 18 years.
For elderly people: BMI norms may be slightly higher (23-28) due to age-related changes in body composition.
For athletes: BMI may be inaccurate due to high percentage of muscle mass. Additional body composition assessment is recommended.
For pregnant women: BMI is calculated based on pre-pregnancy weight. During pregnancy, special weight gain norms are used.
Recommendations for Weight Correction and Healthy Lifestyle
For underweight: increase caloric intake, consume protein products, healthy fats. Consult an endocrinologist to exclude diseases.
For overweight: reduce calories by 300-500 kcal, increase physical activity, control portions, keep a food diary.
For obesity: comprehensive approach with doctor, nutritionist and physical therapist. Possible medication therapy or surgical treatment.
General principles of healthy eating: balanced diet with vegetables, fruits, whole grain products, lean proteins. Limiting sweets, fatty foods and alcohol.
BMI Limitations and Alternatives
BMI disadvantages: does not account for fat tissue distribution, muscle mass, bone density, ethnic body structure features.
Alternative assessment methods: waist circumference measurement, waist-to-hip ratio, bioimpedance analysis, DEXA scanning.
Waist circumference as additional indicator: for men — up to 94 cm (normal), over 102 cm (high risk); for women — up to 80 cm (normal), over 88 cm (high risk).
Benefits of Online BMI Calculator
✓ Instant calculation using WHO formula
✓ Detailed result interpretation
✓ Personalized weight correction recommendations
✓ Consideration of user's gender and age
✓ Free use without registration
✓ Adapted interface for mobile devices
Regularly monitor your BMI to maintain optimal weight and preserve health. Remember that BMI is an approximate indicator, and for comprehensive health assessment, consultation with a doctor is recommended.