Calculate your Body Mass Index with metric or imperial units. See your BMI category, healthy weight range, and visual scale indicator.
Your BMI
Normal weight
BMI Scale
Healthy Weight Range
56.7 – 76.3 kg
BMI 18.5 – 24.9
BMI was invented by Belgian mathematician Adolphe Quetelet in 1832 as a simple way to classify body weight relative to height. For metric units, divide weight in kilograms by height in meters squared. A 70 kg person at 175 cm (1.75 m) has a BMI of 70 / (1.75)² = 22.9. For imperial units, the formula is (weight in pounds × 703) / (height in inches)². The WHO adopted BMI as the international standard for classifying weight status in adults.
Underweight: BMI < 18.5
Normal weight: BMI 18.5 – 24.9
Overweight: BMI 25.0 – 29.9
Obese: BMI ≥ 30.0
These thresholds are based on large population studies showing increased health risks at higher BMI values. A BMI of 25 is associated with increased risk of cardiovascular disease, type 2 diabetes, and certain cancers. However, some Asian health organizations use lower thresholds (23 for overweight, 27.5 for obese) due to higher body fat percentages at equivalent BMI values.
BMI cannot distinguish between muscle and fat. A bodybuilder with 5% body fat may register as “obese” by BMI. It also does not account for fat distribution — visceral fat (around organs) is far more dangerous than subcutaneous fat (under skin). Waist-to-hip ratio and waist circumference are better predictors of metabolic risk. BMI was designed for population-level screening, not individual diagnosis. For a complete health assessment, combine BMI with body composition measurements and medical consultation.
The standard BMI thresholds were developed from studies of European populations. Research shows significant ethnic variation: South Asian populations develop metabolic complications at lower BMI values (23-24), while Polynesian populations may be metabolically healthy at higher BMI values. Japan and China use BMI 25 as the obesity threshold (vs. 30 in Western countries). The WHO recommends that countries establish population-specific action points while maintaining the international classification for global comparisons.
No. BMI does not distinguish between muscle and fat mass. Athletes with high muscle mass often have BMI values in the “overweight” or “obese” range despite being very lean. For these individuals, body fat percentage (measured by DEXA scan, calipers, or bioimpedance) is a much better indicator of health status.
A “normal” BMI of 18.5-24.9 corresponds to different weight ranges depending on height. For someone 170 cm (5'7") tall, the healthy range is approximately 53-72 kg (117-159 lbs). For 180 cm (5'11"), it is 60-81 kg (132-179 lbs). This calculator shows your personalized healthy weight range based on your height.
Standard BMI categories are for adults aged 20+. For children and teens (ages 2-19), BMI is calculated the same way but interpreted using age and sex-specific percentile charts from the CDC or WHO. A child at the 85th percentile is considered overweight, and at the 95th percentile, obese. This calculator is designed for adults.