How BMI is calculated
Body Mass Index is calculated by dividing your weight in kilograms by the square of your height in metres:
BMI = weight (kg) ÷ height² (m²)
Example: 85 kg ÷ (1.80 m)² = 85 ÷ 3.24 = 26.2
The formula was originally developed by Belgian mathematician Adolphe Quetelet in the 19th century as a population-level statistical tool — not as a diagnostic measure for individual health. It has since become one of the most widely used clinical screening tools worldwide, despite significant known limitations.
BMI categories for men
| BMI range | Category | Health implication |
|---|---|---|
| Below 18.5 | Underweight | Risk of nutrient deficiency, bone loss |
| 18.5 – 24.9 | Normal weight | Lowest risk of weight-related disease |
| 25.0 – 29.9 | Overweight | Moderately elevated risk |
| 30.0 – 34.9 | Obese (Class I) | Significantly elevated risk |
| 35.0 and above | Obese (Class II/III) | High to very high risk |
What is a good BMI for men specifically?
The standard healthy range of 18.5–24.9 applies to men as well as women. However, research suggests that men at the upper end of the normal range (23–24.9) and into the low overweight range (25–27) may have similar health outcomes to those in the middle of the normal range, particularly when they are physically active and have relatively low abdominal fat.
For most men, a BMI between 20 and 25 represents an optimal target in terms of cardiovascular risk, metabolic health, and overall mortality. Very lean men (BMI below 20) may face increased risk of osteoporosis and immune function issues over time.
Why BMI is misleading for muscular men
BMI cannot distinguish between muscle and fat. A man who is 180 cm and 90 kg with 12% body fat would have a BMI of 27.8 — classified as overweight — yet be in excellent health with very low metabolic risk. Conversely, a man with the same BMI who carries most of his weight as visceral abdominal fat has significantly elevated health risks.
Research estimates that BMI misclassifies the health status of approximately 30–40% of men who exercise regularly. If you lift weights or engage in significant physical activity, pair your BMI reading with a body fat percentage measurement for a more accurate picture.
Better indicators of health for men
For men, waist circumference is often a better predictor of metabolic risk than BMI. A waist measurement above 94 cm (37 inches) indicates elevated risk; above 102 cm (40 inches) indicates high risk for conditions including type 2 diabetes and cardiovascular disease, regardless of BMI.
Body fat percentage gives a more precise picture of adiposity. Healthy body fat for men is generally 10–20%, with athletic individuals typically in the 6–13% range. Body fat above 25% in men is associated with increased metabolic risk.
Waist-to-height ratio (waist circumference divided by height) below 0.5 is associated with lower cardiovascular risk and is considered by some researchers to be more accurate than BMI as a screening tool.
How men can reach and maintain a healthy BMI
- Prioritise resistance training 2–4 times per week — building muscle improves body composition even if BMI does not change dramatically.
- Eat a high-protein diet (1.6–2g per kg of body weight) to preserve or build lean mass while reducing fat.
- Reduce alcohol consumption — alcohol is calorie-dense and lowers testosterone, increasing fat accumulation.
- Maintain a 300–500 kcal daily deficit if weight loss is the goal, rather than extreme restriction.
- Monitor waist circumference alongside BMI for a more complete health picture.