BMI Calculator
Calculate your Body Mass Index (BMI) and see your weight category.
The BMI Calculator computes your Body Mass Index — a number used by healthcare systems worldwide as a first-pass screening indicator for weight status. Enter your weight and height in metric (kg/cm) or imperial (lbs/inches) to get your BMI score and the corresponding WHO weight category. BMI is a useful population-level tool precisely because it is fast and requires no equipment — but it has well-documented limitations: it does not distinguish between muscle and fat, does not account for age, sex, or ethnicity differences in body composition, and can misclassify muscular athletes as overweight and elderly adults as normal weight when they have lost muscle mass. Many health organizations in Asia — including those in China, Japan, South Korea, Hong Kong, and Singapore — use different (lower) BMI cutoffs because studies show higher metabolic risk at lower BMI values in Asian populations. Use this result as a starting point for conversation with a healthcare provider, not as a standalone health verdict.
BMI Calculator
Formula
Examples
70 kg, 175 cm — Adult Male
Within normal WHO range.
→ BMI: 22.9 | Category: Normal weight (WHO) | Also normal by Asia-Pacific standards (below 23)
85 kg, 170 cm — Overweight Example
Overweight by WHO; also overweight by Asia-Pacific standards.
→ BMI: 29.4 | Category: Overweight (WHO: 25–29.9) | Also overweight by Asia-Pacific standard (above 27.5)
55 kg, 165 cm — Normal Weight
Common adult female scenario.
→ BMI: 20.2 | Category: Normal weight (both WHO and Asia-Pacific)
100 kg, 180 cm — Obese Range
Illustrates Class I obesity threshold.
→ BMI: 30.9 | Category: Obese Class I (WHO) | Strongly recommended to consult healthcare provider
175 lbs, 5'10' — Imperial Calculation
US measurement example.
→ BMI: 25.1 | Category: Overweight (just above WHO normal range of 18.5–24.9)
Tips
- ✓BMI is a screening tool, not a diagnosis. A result outside the normal range is a reason to talk to a doctor, not a conclusion.
- ✓If you are of East Asian, South Asian, or Southeast Asian descent, the Asia-Pacific thresholds (normal below 23, overweight 23–27.4) may be more relevant to your health risk.
- ✓Waist circumference is a useful complement to BMI — WHO guidelines suggest risk increases above 80 cm (women) and 94 cm (men); for Asian populations, the thresholds are often 80 cm (women) and 90 cm (men).
- ✓Muscular individuals should not over-interpret a high BMI — body fat percentage testing (DEXA, hydrostatic weighing) provides a more meaningful measurement.
- ✓For children under 18, do not use adult BMI categories. Consult growth chart percentiles appropriate for the child's age and sex.
- ✓BMI naturally changes with age. Many guidelines suggest a slightly higher normal BMI range may be acceptable for adults over 65 due to protective effects.
Frequently Asked Questions
What is BMI and what does it measure?
BMI (Body Mass Index) is a number derived from your weight and height. It is used as a population-level screening indicator for underweight, normal weight, overweight, and obesity. BMI does not directly measure body fat percentage, body composition, fitness level, or metabolic health — it is a proxy measurement, not a diagnostic.
What is the BMI formula?
Metric: BMI = weight (kg) ÷ height² (m²). Example: 70 kg, 1.75 m → BMI = 70 ÷ 3.0625 = 22.9. Imperial: BMI = 703 × weight (lbs) ÷ height² (inches²). Example: 154 lbs, 69 inches → BMI = 703 × 154 ÷ 4761 = 22.7.
What are the WHO BMI categories?
WHO standard categories: Under 18.5 = Underweight | 18.5–24.9 = Normal weight | 25.0–29.9 = Overweight | 30.0–34.9 = Obese Class I | 35.0–39.9 = Obese Class II | 40.0+ = Obese Class III (Severe obesity). These thresholds are based on studies primarily conducted on European populations.
Do Asian populations use different BMI cutoffs?
Yes. Multiple health organizations in Asia recommend adjusted thresholds due to evidence that Asian populations face higher metabolic risks (type 2 diabetes, cardiovascular disease) at lower BMI values. Common Asian-Pacific reference ranges: Under 18.5 = Underweight | 18.5–22.9 = Normal | 23–27.4 = Overweight | 27.5+ = Obese. The World Health Organization has acknowledged these differences and published expert consultation reports on the topic.
Is BMI accurate for athletes and muscular people?
BMI significantly overestimates obesity risk in athletes. Muscle is much denser than fat — a 90 kg rugby player and a 90 kg sedentary person have the same BMI but very different health profiles. For people with high muscle mass, body fat percentage, waist circumference, or DEXA scan data are better indicators of health risk than BMI.
Is BMI accurate for older adults?
BMI can underestimate health risk in older adults, who tend to lose muscle mass (sarcopenia) while fat mass stays the same or increases. An older adult with a "normal" BMI may have high body fat percentage due to low muscle mass. Healthcare providers often use BMI alongside other assessments (grip strength, waist circumference) in older patients.
What is a healthy BMI for children?
Adult BMI categories do not apply to children and teens. For those under 18, BMI is plotted on age- and sex-specific growth charts as a percentile, not compared to fixed thresholds. A pediatrician or school health service should interpret children's BMI results.
What should I do if my BMI is outside the normal range?
A BMI result outside the normal range is a reason to consult a healthcare professional, not a diagnosis. A doctor or dietitian can put your BMI in context alongside other health indicators — blood pressure, fasting glucose, lipid panel, waist circumference, and activity level — to give a meaningful health picture.
Related Calculators
Unit Converter
PopularConvert between common units of length, weight, temperature, area, and volume.
Conversion ToolsAge Calculator
PopularCalculate your exact age in years, months, and days from your birth date.
Date & TimeAverage Calculator
Calculate the mean, median, mode, and range of a set of numbers.
Math & NumbersDisclaimer: BMI is a general screening indicator and does not account for muscle mass, bone density, age, sex, ethnicity, or body fat distribution. This calculator is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional for health assessments.