Calculate your Body Mass Index (BMI) instantly. Find your weight category and healthy weight range for your height.
A BMI calculator determines Body Mass Index, a screening measure that estimates whether your weight is healthy relative to your height. It divides weight in kilograms by height in meters squared, then places the result into categories such as underweight, normal, overweight, or obese, based on World Health Organization thresholds.
22.9
Your BMI
70 kg
Your weight
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BMI Calculator
Body Mass Index (BMI) is a widely used screening tool calculated using the formula: BMI = weight (kg) / height² (m). Despite its simplicity, BMI remains the standard metric used by the WHO and most health organisations to classify body weight at the population level.
The WHO defines these categories for adults: below 18.5 — underweight, 18.5–24.9 — normal weight, 25.0–29.9 — overweight, 30.0–34.9 — obesity class I, 35.0–39.9 — class II, 40+ — class III (severe).
Limitations
BMI is a useful screening tool but does not directly measure body fat. Athletes with high muscle mass may fall into the "overweight" category despite having low body fat. Conversely, individuals with a normal BMI can still carry excess visceral fat, particularly with a sedentary lifestyle.
For a more accurate assessment: waist circumference (risk threshold: 80 cm for women, 94 cm for men), waist-to-hip ratio, and body fat percentage via bioelectrical impedance analysis or DEXA scan.
Healthy Weight
Maintaining a BMI in the 18.5–24.9 range is associated with lower risk of hypertension, type 2 diabetes, cardiovascular disease, and certain cancers. At BMI above 30, the risk of these conditions rises substantially.
The WHO recommends at least 150–300 minutes of moderate-intensity aerobic activity per week for adults. If your BMI is above 30 or you have existing health conditions, consult a doctor before starting any weight-loss programme.
Limitations
BMI is a screening tool, not a diagnosis. It uses only height and weight, so it cannot distinguish muscle mass from fat mass — very muscular people (athletes, bodybuilders) are often classified as "overweight" or "obese" by BMI despite having low body fat — our body fat calculator gives a more direct estimate for these cases, while people with low muscle mass and high body fat ("skinny fat") can show a "normal" BMI while still carrying health risk.
BMI thresholds were derived primarily from European population data and apply less precisely across all ethnicities — some health authorities recommend lower overweight/obesity cutoffs for South Asian populations, who show elevated cardiometabolic risk at lower BMI values. BMI also becomes less reliable at the extremes of adult age: in older adults, BMI does not account for age-related muscle loss (sarcopenia), and in growing children and teenagers, BMI is interpreted using age- and sex-specific percentile charts, not the fixed adult categories used here.
Children & Teens
The fixed adult BMI categories (underweight, normal, overweight, obese) do not apply to children and teenagers, whose body composition changes constantly as they grow. Instead, pediatricians use BMI-for-age percentile charts, published separately for boys and girls, that compare a child's BMI to others of the same age and sex.
A child is typically considered to have a healthy weight between the 5th and 85th percentile for their age and sex, overweight between the 85th and 95th percentile, and obese above the 95th percentile. Because these percentiles shift throughout childhood and adolescence, a pediatrician or growth chart — not the adult calculator on this page — should be used to assess a child's weight status.
Key Facts
Below 18.5 — Underweight
May indicate malnutrition or underlying illness. Consult a doctor.
18.5–24.9 — Normal weight
The optimal range for most adults, associated with the lowest health risk.
25.0–29.9 — Overweight
Moderately elevated risk. Small lifestyle changes can have a significant impact.
30+ — Obese
Significantly elevated chronic disease risk. Medical consultation recommended.
BMI in children
For those under 18, BMI is interpreted using age- and sex-specific percentile charts.
Waist circumference
Risk threshold: 80 cm for women, 94 cm for men — regardless of BMI.
A BMI between 18.5 and 24.9 is considered normal weight. Below 18.5 is underweight, 25-29.9 is overweight, and 30 or above is obese.
BMI = weight (kg) / height² (m). For example, a person weighing 70 kg at 1.75 m has a BMI of 70 / (1.75 × 1.75) = 22.9.
BMI is a useful screening tool but has limitations. It may overestimate body fat in athletes and underestimate it in older adults. Consult a healthcare provider for a complete assessment.
A BMI of 25.0 to 29.9 is classified as overweight. A BMI of 30.0 or higher is classified as obese.
Achieving a healthy BMI typically involves a balanced diet and regular physical activity. Even modest weight loss of 5-10% can significantly improve health outcomes.
No. This calculator uses fixed adult BMI categories that don't apply to growing children and teenagers. Pediatric BMI is assessed using age- and sex-specific percentile charts instead — ask your child's doctor or use a pediatric growth chart calculator.
Yes, by the standard WHO classification, 25.0 is the threshold where the "overweight" category begins (18.5-24.9 is "normal weight"). A BMI of 24.9 and a BMI of 25.0 represent a very small real difference in weight, so the category label alone shouldn't be treated as a precise health verdict.