What Is BMI?
Body Mass Index is a number derived from height and weight. It is the most widely used population-level screening tool for weight status.
Metric: BMI = weight (kg) ÷ height (m)²
Imperial: BMI = 703 × weight (lbs) ÷ height (in)²
For the full background on BMI — history, WHO categories, and limitations — see the BMI Calculator.
BMI Categories
| Category | BMI |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese (Class I) | 30.0 – 34.9 |
| Severely Obese (Class II+) | 35.0 and above |
Body Fat Percentage for Men
The Deurenberg formula estimates body fat percentage from BMI and age, with a sex-specific constant for men:
BF% = 1.20 × BMI + 0.23 × Age − 16.2
Men’s body fat categories:
| Category | Body Fat % |
|---|---|
| Essential fat | 2 – 5% |
| Athletes | 6 – 13% |
| Fitness | 14 – 17% |
| Acceptable | 18 – 24% |
| Obese | 25% and above |
Men naturally carry less body fat than women at the same BMI. The constant −16.2 in the male formula (vs −5.4 for women) accounts for this difference.
Ideal Weight for Men
The ideal weight range shown is the body weight that would place you in the normal BMI range (18.5–24.9) for your height:
Min = 18.5 × height (m)²
Max = 24.9 × height (m)²
This is a range, not a single target — any weight within it is consistent with a healthy BMI. For a 5 ft 10 in (178 cm) man, that range is approximately 129–173 lbs (58–79 kg).
Limitations of BMI for Men
BMI is particularly prone to misclassification in men with high muscle mass:
- Muscle vs fat — BMI measures total mass relative to height. A muscular man can score in the overweight range despite having low body fat.
- Abdominal fat — BMI does not capture where fat is stored. Men disproportionately accumulate visceral fat around the abdomen, which carries greater metabolic risk. A waist circumference above 40 in (102 cm) is an independent risk indicator regardless of BMI.
- Age — Body composition changes with age; the same BMI reflects higher fat percentage in older men.
For a more complete picture, use BMI alongside waist circumference or waist-to-height ratio.
Sources
- Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. Br J Nutr. 1991;65(2):105–114.
- World Health Organization. Obesity and overweight.
- National Heart, Lung, and Blood Institute. Calculate Your Body Mass Index.