Loading page
Calculate your Body Mass Index in seconds
Enter your height and weight to calculate your BMI and see which WHO category you fall into. Supports both metric (kg/cm) and imperial (lbs/ft-in) units.
Enter your details below and click Calculate to see your results.
Body Mass Index (BMI) is a simple screening measure that estimates body fat based on your height and weight. It was developed by Belgian mathematician Adolphe Quetelet in the 1830s and is calculated by dividing your weight in kilograms by the square of your height in metres (BMI = kg/m²). The World Health Organization (WHO) uses BMI to classify adults into weight categories: underweight (below 18.5), normal weight (18.5–24.9), overweight (25.0–29.9), and obese (30.0 and above). While BMI is widely used in public health research and clinical screening, it is a starting point — not a definitive diagnosis of health.
BMI does not distinguish between muscle mass and fat mass, which means athletes and people with high muscle mass may be classified as overweight or obese despite having low body fat. It also does not account for age, sex, ethnicity, or body fat distribution. For example, older adults tend to have more body fat than younger adults at the same BMI, and women typically carry more body fat than men. Research has also shown that BMI thresholds may not apply equally across ethnic groups — some Asian populations face higher health risks at lower BMI values. For a more complete picture of your health, consider combining BMI with other measures such as waist circumference, body fat percentage, or waist-to-hip ratio.
A BMI under 18.5 is classified as underweight and may indicate nutritional deficiency or an underlying health condition. A BMI between 18.5 and 24.9 is considered normal weight and is generally associated with the lowest health risks. A BMI of 25.0 to 29.9 falls in the overweight range, which may increase the risk of conditions like type 2 diabetes and cardiovascular disease. A BMI of 30.0 or above is classified as obese, with Class I (30–34.9), Class II (35–39.9), and Class III (40+) indicating progressively higher health risks. Remember that BMI is one data point — your overall health depends on many factors including diet, physical activity, sleep, and genetics.
While BMI is a useful starting point, several other metrics can give you a more accurate picture of your body composition and health. Body fat percentage, measured via skinfold calipers, bioelectrical impedance, or DEXA scans, directly quantifies how much of your weight is fat versus lean tissue. Waist circumference is a simple measure of abdominal fat — a waist over 102 cm (40 in) for men or 88 cm (35 in) for women is associated with increased metabolic risk. The waist-to-hip ratio compares your waist and hip measurements to assess fat distribution. Lean body mass calculators estimate your fat-free weight using validated formulas. For the most complete assessment, combine multiple metrics and consult with a healthcare professional.
Mark is a 35-year-old male who stands 5'10" (178 cm) and weighs 185 lbs (84 kg). He wants to check his BMI to understand where he falls on the WHO classification scale.
With a BMI of 26.5, Mark falls into the Overweight category (25.0–29.9). His healthy weight range for his height is approximately 58.6–78.9 kg (129–174 lbs). This does not necessarily mean Mark is unhealthy — if he exercises regularly and carries significant muscle mass, his BMI may overestimate his body fat. A good next step would be to check his body fat percentage or waist circumference for a more complete picture. If he does want to reduce his BMI, a modest calorie deficit of 300–500 calories per day combined with strength training can help him lose fat while preserving muscle.
Common questions about this calculator and how to use your results.
A healthy BMI range is 18.5 to 24.9, according to the World Health Organization. This range is associated with the lowest risk of weight-related health problems for most adults. However, the "healthy" range can vary by age, sex, and ethnicity. For example, some health organizations recommend a BMI range of 18.5–23.0 for Asian populations due to higher metabolic risk at lower BMI values.
BMI is calculated by dividing your weight in kilograms by the square of your height in metres: BMI = weight (kg) ÷ height (m)². For example, if you weigh 70 kg and are 1.75 m tall, your BMI is 70 ÷ (1.75 × 1.75) = 22.9. If you use imperial units, the formula is BMI = (weight in pounds × 703) ÷ (height in inches)². Our calculator handles the conversion automatically — just enter your measurements in whichever unit system you prefer.
BMI is often inaccurate for athletes and highly muscular individuals because it cannot distinguish between muscle mass and fat mass. Muscle is denser than fat, so a muscular person may have a high BMI while having a low body fat percentage. For athletes, body fat percentage (measured via DEXA scan, skinfold calipers, or bioelectrical impedance) is a more accurate indicator of body composition than BMI alone.
The WHO defines six BMI categories for adults: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25.0–29.9), Obese Class I (30.0–34.9), Obese Class II (35.0–39.9), and Obese Class III (40.0 and above). Each category reflects a different level of health risk, with higher BMI values generally associated with greater risk of conditions like type 2 diabetes, heart disease, and certain cancers.
The standard BMI formula does not adjust for age or gender, but interpretation should consider both. Older adults tend to have more body fat and less muscle than younger adults at the same BMI, so a slightly higher BMI (25–27) may be acceptable for people over 65. Women naturally carry more body fat than men, so a woman and a man with the same BMI may have different body fat percentages. For children and teens, BMI is plotted on age- and sex-specific growth charts and expressed as a percentile rather than a fixed number.
To lower your BMI, focus on sustainable fat loss through a moderate calorie deficit (300–500 calories below your maintenance level), regular physical activity (both cardio and strength training), and a balanced diet rich in protein, fibre, and whole foods. Aim to lose 0.5–1 kg (1–2 lbs) per week for safe, sustainable results. Crash diets and extreme calorie restriction can lead to muscle loss, nutrient deficiencies, and metabolic slowdown. Use our calorie deficit calculator and macro calculator to build a personalised plan.
Explore more calculators and recipes to support your goals.