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Body Mass Index

Calculate Your Body Mass Index

Enter your height and weight to get your BMI, category, and personalized health advice — instantly, for free.

yrs
BMI Standard
cm
kg
0.0kg/m²
Weight Category
Normal
WHO Global Standard

Health Advice

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What Is BMI?

BMI (Body Mass Index) is an internationally used screening measure to assess body weight relative to height. The formula is: BMI = weight (kg) ÷ height (m)². It provides a quick, cost-free estimate of whether a person's weight might pose health risks.

BMI does not distinguish between muscle and fat mass. Athletes, pregnant women, the elderly, and children should use additional metrics and consult a healthcare professional for a complete assessment.

People of Asian descent are at higher health risk at lower BMI values. The Asian standard — recommended by the World Health Organization for Asian populations — sets the overweight threshold at 23 and obesity at 27.5 for risk stratification; the Chinese national standard (used in this calculator's "Asian Standard" mode) sets overweight at 24 and obesity at 28.

< 18.5
Underweight
18.5 – 24.9
Normal Weight
25 – 29.9
Overweight
≥ 30
Obese

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Frequently Asked Questions

What is a healthy BMI for adults?
For adults, a healthy BMI is 18.5 to 24.9 (WHO Global standard). Below 18.5 is underweight; 25–29.9 is overweight; 30 and above is obese. Using the Asian standard, the healthy range is 18.5–23.9, with overweight at 24–27.9 and obesity at ≥28.
How do you calculate BMI?
BMI = weight in kg ÷ (height in m)². For example, someone who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9 — in the normal range. In imperial units: BMI = (weight in lbs × 703) ÷ (height in inches)².
Is BMI accurate for everyone?
BMI is a useful first-pass screening tool but has known limitations. It cannot distinguish between fat and lean muscle mass, so muscular athletes may test as overweight despite being healthy. It is also less reliable for children (who need age-specific percentile charts), adults over 65, and pregnant women. Use it alongside waist circumference, body fat percentage, or clinical assessment for a more complete picture.
Does BMI differ for men and women?
The BMI classification thresholds are identical for men and women, but women naturally carry a higher percentage of body fat at the same BMI. This means that at the same BMI, a woman typically has more fat mass than a man. For a more sex-specific assessment, consider body fat percentage measurements.
How is BMI calculated for children and teenagers?
Children and adolescents (ages 2–19) are evaluated using BMI-for-age percentile charts, not fixed cut-off numbers, because healthy body fat levels change significantly during growth. A child is underweight if below the 5th percentile, healthy weight at the 5th–84th percentile, overweight at the 85th–94th percentile, and obese at or above the 95th percentile. Always use validated pediatric charts (CDC or WHO) or consult a pediatrician.
What is a good BMI for people over 65?
Research indicates that for adults aged 65 and over, a slightly higher BMI range of 22–27 may be associated with better outcomes. Being underweight in older age significantly increases the risk of bone fractures, nutritional deficiency, and loss of muscle mass (sarcopenia). Older adults should seek personalized advice from their physician.
Why does the Asian BMI standard have lower thresholds?
Studies show that people of Asian descent develop obesity-related health risks (type 2 diabetes, cardiovascular disease, hypertension) at lower BMI values compared to Caucasian populations — likely due to differences in body fat distribution, particularly higher visceral fat at equivalent BMI levels. The Chinese national standard therefore sets the overweight threshold at 24 (vs. 25 for WHO) and obesity at 28 (vs. 30).
How do I lower my BMI?
Sustainable BMI reduction involves a moderate calorie deficit (typically 500 kcal/day for ~0.5 kg/week weight loss), prioritizing whole foods (lean protein, vegetables, whole grains), limiting added sugars and ultra-processed foods, and combining aerobic exercise (150+ minutes/week of moderate intensity) with resistance training. Crash diets are not recommended — they cause rapid muscle loss and are rarely maintained. Consult a registered dietitian for a personalized plan.

Maintaining a Healthy BMI

Balanced diet: Focus on whole foods — vegetables, fruits, lean proteins (fish, chicken, legumes), and complex carbohydrates (oats, brown rice, sweet potatoes). Limit ultra-processed foods, refined sugars, and saturated fats.

Regular physical activity: Aim for at least 150 minutes of moderate-intensity aerobic activity per week (brisk walking, cycling, swimming), plus two sessions of strength training to preserve muscle mass.

Sleep and stress: Poor sleep and chronic stress elevate cortisol, which promotes fat storage and increases appetite. Prioritize 7–9 hours of quality sleep per night and practice stress-management techniques such as mindfulness or regular exercise.

Hydration: Drinking adequate water supports metabolism and can reduce caloric intake when consumed before meals. Adults generally need 2–3 litres per day depending on activity level and climate.

Medical check-ups: BMI is one data point. Regular check-ups that include blood pressure, fasting glucose, cholesterol, and waist circumference give a much more complete picture of metabolic health.