What is a healthy BMI?

According to the World Health Organization, a healthy adult BMI is between 18.5 and 24.9 kg/m².

Why does BMI not work well for bodybuilders?

BMI measures total mass without distinguishing between dense muscle tissue and fat mass. A lean athlete can register as 'overweight' due to high muscularity.

Body MetricsScope: Adults (18+)

BMI Calculator

Calculate Body Mass Index according to World Health Organization criteria

Input Parameters

Real-time calculation updates dynamically as you adjust inputs. Values remain strictly local on your device.

Body Mass Index (BMI)Normal weight

22.9kg/m²

WHO Classification: Normal weight

BMI Prime

0.92

Ratio relative to normal upper limit (25.0)

Healthy Weight Range

56.7 – 76.3kg

Ponderal Index

13.06kg/m³

WHO Adult BMI Categories

< 18.5

Underweight

Increased risk of nutritional deficiency

18.5 – 24.9

Normal weight

Lowest statistical all-cause mortality

25.0 – 29.9

Overweight

Mildly elevated cardiometabolic risk

30.0 – 34.9

Obese Class I

Moderate health risk

35.0 – 39.9

Obese Class II

High health risk

≥ 40.0

Obese Class III

Severe health risk

Clinical Responsibility Note: BMI is a population-level screening metric. It does not directly quantify body composition or distinguish between adipose tissue and skeletal muscle mass.

Mathematical Formula & Scientific Methodology

Formula: Quetelet Adult Body Mass Index

BMI = weight (kg) / [height (m)]²

Developed in the 19th century by Adolphe Quetelet, BMI scales weight by height squared to normalize across human statures.

Model Assumptions

Assumes adult human physiology (age ≥ 18)
Assumes typical proportion of skeletal muscle

Variables & Standard Units

Symbol	Physiological Meaning	Unit
weight	Body mass in kilograms	kg
height	Stature in meters	m

Scientific Limitations

Overestimates adiposity in muscular athletes
Underestimates adiposity in elderly with sarcopenia

Peer-Reviewed Scientific Citations

Obesity: preventing and managing the global epidemic. Report of a WHO consultation (2000)

World Health Organization (2000) — WHO Technical Report Series, 894, 1-253

Key Finding: Standard international adult BMI classifications: Underweight (<18.5), Normal (18.5-24.9), Overweight (25.0-29.9), Obesity Class I (30.0-34.9), Class II (35.0-39.9), Class III (>=40.0).

Frequently Asked Questions

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