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Calculate your BMI: formula, table and interpretation

Calculate your Body Mass Index (BMI) and interpret your result according to WHO thresholds. Formula and reference table.

Published on January 13, 2026

Body Mass Index (BMI) is the most widely used indicator in the world to assess whether a person's weight is appropriate for their height. Although imperfect (it does not distinguish between muscle mass and fat mass), it remains the international medical reference for defining overweight and obesity thresholds.

Understanding the conversion

BMI is calculated by dividing weight in kilograms by the square of height in meters. The WHO (World Health Organization) has defined universal thresholds to classify the result. These thresholds apply to adults aged 18 to 65. For children, elderly people, pregnant women and elite athletes, interpretation should be adapted.

📐 Formula

BMI = Weight (kg) / [Height (m)]² or BMI = Weight (lbs) × 703 / [Height (inches)]²

📊 Conversion table

BMI	WHO Category	Associated risks
< 16.0	Severe underweight	Malnutrition, deficiencies
16.0 – 18.5	Underweight	Nutritional deficiencies
18.5 – 25.0	Normal weight	Minimal risk
25.0 – 30.0	Overweight	Slightly increased risk
30.0 – 35.0	Obesity class 1	High risk
35.0 – 40.0	Obesity class 2	Very high risk
> 40.0	Obesity class 3 (morbid)	Extreme risk

💡 Practical examples

Example 1: person weighing 154 lbs, height 5'9" (175 cm)

BMI = 154 × 703 / (69)² = 108,262 / 4,761 = 22.7. Category: normal weight. Optimal result according to WHO.

Example 2: person weighing 198 lbs, height 5'7" (170 cm)

BMI = 198 × 703 / (67)² = 139,194 / 4,489 = 31.0. Category: obesity class 1. Ideal weight range for this height: 118–159 lbs.

Example 3: BMI limitations for athletes

An athlete weighing 187 lbs and 6'0" tall has BMI = 25.4 (overweight). But their body fat is low and muscle mass is high. BMI alone is insufficient for athletes.