BMI is a useful population-level screening tool, but it has limitations. It does not distinguish between muscle and fat — so muscular athletes may have a high BMI without excess body fat. It is also less accurate for older adults and some ethnic groups. Use it alongside body fat percentage and waist circumference for a fuller picture.

How do I calculate BMI?

BMI = weight (kg) ÷ height (m)². For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9.

What BMI is considered obese?

A BMI of 30.0 or above is classified as obese. Obese Class I is 30–34.9, Obese Class II is 35–39.9, and Obese Class III (severe obesity) is 40 and above.

Does BMI differ for men and women?

The standard BMI formula uses the same thresholds for men and women. However, women typically have more body fat than men at the same BMI. Some clinicians use sex-specific norms, but the WHO standard 18.5–24.9 healthy range applies to both.

BMI Calculator — Free Body Mass Index Tool (2026)

Q: What is a healthy BMI?

According to the CDC and WHO, a healthy BMI for adults is 18.5–24.9. Below 18.5 is underweight, 25.0–29.9 is overweight, and 30.0 or above is considered obese.

⚖️ BMI Calculator

CDC-standard classification · Metric & imperial · Healthy weight range included

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BMI Value—

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Healthy Weight Range—

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Underweight (<18.5)Normal (18.5–24.9)Overweight (25+)Obese (30+)

📋 Evidence-Based Recommendations

⚠️ BMI is a screening tool, not a diagnosis. Athletes with high muscle mass may have an elevated BMI without excess body fat. Consult a healthcare professional for clinical assessment.

BMI Chart — Weight Categories for Adults

The following BMI ranges are defined by the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) for adults aged 20 and above.

BMI Range	Category	Health Risk
Below 18.5	Underweight	Malnutrition, osteoporosis, immune deficiency
18.5 – 24.9	Normal Weight	Lowest risk for most chronic diseases
25.0 – 29.9	Overweight	Moderate increased risk for metabolic disease
30.0 – 34.9	Obese Class I	High risk — lifestyle intervention recommended
35.0 – 39.9	Obese Class II	Very high risk — medical support recommended
40.0 and above	Obese Class III	Extremely high risk — specialist care indicated

BMI Formula — How Is It Calculated?

Body Mass Index is calculated by dividing weight in kilograms by height in metres squared:

BMI = Weight (kg) ÷ Height (m)²

Example: A person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9 — Normal Weight.

Limitations of BMI

BMI is useful for population-level screening but has well-documented limitations:

Muscle vs. fat: A muscular athlete may have a BMI in the overweight range despite having low body fat. For these individuals, body fat percentage is a more meaningful metric.
Age: Older adults tend to have more fat and less muscle at the same BMI. Some clinicians use age-adjusted norms for adults over 65.
Ethnicity: Some research suggests different BMI thresholds may be more appropriate for South Asian, East Asian, and Middle Eastern populations, who tend to accumulate visceral fat at lower BMI values.
Sex: Women have more essential body fat than men at the same BMI, but standard WHO thresholds apply to both sexes.

For a more comprehensive picture, use BMI alongside body fat percentage and waist-to-hip ratio.

What Is a Healthy BMI for Women?

The standard healthy BMI range for adult women is 18.5–24.9, the same as for men. However, women naturally carry more essential body fat (12–15%) compared to men (3–5%), so the health implications at the same BMI may differ slightly. Consult our body fat calculator for a sex-specific assessment.

What Is a Healthy BMI for Men?

A healthy BMI for adult men is also 18.5–24.9. Men tend to accumulate more visceral (abdominal) fat than women, which is the most metabolically harmful type. If your BMI is in the overweight range, check your waist-to-hip ratio for a cardiovascular risk assessment.

How to Lower Your BMI

If your BMI is in the overweight or obese range, even a modest 5–10% reduction in body weight meaningfully improves metabolic health markers (blood pressure, insulin sensitivity, cholesterol). Evidence-based strategies include:

A sustained calorie deficit of 300–500 kcal/day — use our TDEE calculator to find your target
Prioritising protein intake (1.2–1.6 g/kg bodyweight) to preserve muscle during weight loss
Combining resistance training with aerobic exercise for best long-term body composition outcomes
7–9 hours of sleep per night — sleep deprivation drives appetite-stimulating hormones (ghrelin) and suppresses satiety hormones (leptin)

BMI Calculator — Frequently Asked Questions

A healthy BMI for adults is 18.5–24.9 according to the WHO and CDC. This range is associated with the lowest risk of obesity-related chronic diseases. However, individual factors like muscle mass, age, and ethnicity affect how BMI maps to health risk.

BMI is a useful screening tool at the population level, but it cannot distinguish between muscle and fat, making it inaccurate for athletes. For a more accurate individual health assessment, combine BMI with body fat percentage, waist circumference, blood pressure, and fasting blood glucose.

A BMI of 25.0–29.9 is classified as overweight. This range indicates increased risk for cardiovascular disease, type 2 diabetes, and other metabolic conditions, though the absolute risk increase is modest compared to the obese categories.

BMI decreases when you lose body fat. The most effective approach is combining a moderate calorie deficit (300–500 kcal/day below TDEE) with resistance training to preserve muscle mass. Use our free calorie calculator to find your personalised daily target.

Yes — especially for muscular individuals. Some research identifies a group called "metabolically healthy obese" — people with high BMI but normal metabolic markers. However, long-term studies show that metabolic health in this group tends to deteriorate over time. High BMI with good metabolic markers is better than high BMI with poor ones, but lower BMI (through muscle-friendly fat loss) is generally preferable.