Calculate your Body Mass Index in metric or imperial units and see your weight category.
Ages 2-120
Your category is highlighted based on your current BMI.
| BMI Range | Category |
|---|---|
| < 16.0 | Severe Thinness |
| 16.0 – 16.9 | Moderate Thinness |
| 17.0 – 18.4 | Mild Thinness |
| 18.5 – 24.9 | Normal← You |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obese Class I |
| 35.0 – 39.9 | Obese Class II |
| ≥ 40.0 | Obese Class III |
Your BMI indicates a normal, healthy weight.
Stay Active
150+ minutes of moderate exercise per week
Balanced Diet
Rich in fruits, vegetables, and whole grains
Sleep Well
7-9 hours of quality sleep every night
Your BMI is Normal — Take Action
Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any health-related decisions or starting any diet or exercise programme.
Metric: BMI = weight (kg) ÷ height (m)²
Imperial: BMI = 703 × weight (lbs) ÷ height (in)²
BMI Prime: BMI ÷ 25 (ratio to upper normal limit)
Ponderal Index: weight (kg) ÷ height (m)³ — more reliable for very tall/short people
Did you know?
Arnold Schwarzenegger at his peak (1974 Mr. Olympia) had a BMI of approximately 33 — firmly in the "obese" category according to WHO guidelines. Yet he had only 4–5% body fat. This is the most famous example of why BMI alone is an incomplete health metric.
BMI was invented in 1832 by Belgian polymath Adolphe Quetelet, who called it the "Quetelet Index." Quetelet was a statistician and astronomer, not a physician — and he created it purely as a tool to describe population distributions, explicitly stating it should NOT be used for individual assessment. For 140 years, the index was largely ignored as a medical tool. In 1972, American physiologist Ancel Keys re-examined it in a study of 7,500 men across five countries and coined the term "Body Mass Index," showing it correlated better with body fat than other simple measurements. The WHO adopted it as a global obesity screening tool in 1995.
Japan uses a BMI of ≥25 as the threshold for obesity — significantly lower than the WHO's global threshold of 30. This reflects the fact that Japanese people tend to develop metabolic complications at lower BMI values.
Globally, about 2.5 billion adults are overweight (BMI ≥25) and 890 million are obese (BMI ≥30) as of 2022 — more than double the rate in 1990.
At a BMI below 16, starvation-related organ failure becomes a serious medical risk. The body begins breaking down muscle and organ tissue for energy when fat stores are depleted.
The BMI scale ranges from approximately 10 (extreme emaciation) to 70+ (extreme obesity). The highest reliably recorded BMI in a living person was approximately 188 in Jon Brower Minnoch in 1978.
Despite being invented for population statistics, BMI is now used in insurance premiums, military fitness standards, and medical eligibility criteria for procedures like joint replacement surgery — applications its creator never intended.
A 2023 policy statement from the American Medical Association warned against using BMI as the primary measure of health, calling it "an imperfect proxy" that can produce misleading results when used in isolation.
A BMI between 18.5 and 24.9 is considered normal weight by the WHO. Below 18.5 is underweight; 25–29.9 is overweight; 30–34.9 is Class I obese; 35–39.9 is Class II; 40+ is Class III (severe) obesity. Different thresholds apply in some countries — Japan uses ≥25 as obese.
BMI Prime is the ratio of your BMI to the upper limit of normal (25 kg/m²). A value less than 0.74 means underweight, 0.74–1.00 is normal, above 1.00 is overweight, and above 1.20 is obese. It lets you see at a glance how far you are from the healthy ceiling.
The Ponderal Index (PI) uses height³ instead of height², making it more reliable for very tall or very short individuals. A normal PI is around 11–15 kg/m³. Unlike BMI, the PI doesn't overestimate adiposity in tall people or underestimate in short people.
Many. BMI doesn't measure body fat directly — it simply compares weight to height. A muscular athlete with very little fat can have a high BMI (labelled obese), while an inactive person with little muscle but high visceral fat can have a normal BMI. For a fuller picture, use BMI alongside body fat %, waist circumference, and other markers.
Yes, significantly. South and East Asian populations have higher health risks at lower BMIs. The WHO recommends a separate overweight threshold of 23 for Asian populations. Additionally, Black individuals may have higher bone density, meaning their BMI slightly overstates fat relative to the general formula.
Don't panic! BMI is a starting point. Check your waist circumference (>94cm for men / >80cm for women raises risk), get a body fat assessment, and speak with your GP. If you genuinely have excess body fat, even a 5–10% weight reduction delivers substantial health improvements — use the Health Plan link below to build a personalised diet and workout plan.
BMI is a screening tool, not a diagnostic measure. It cannot differentiate between fat and lean tissue, does not account for age or sex differences in body composition, and may misclassify muscular individuals. For a more complete health picture, consider combining BMI with body fat percentage, waist circumference, and blood biomarkers. Always discuss results with a healthcare provider.
Research shows that health risks associated with BMI vary by ethnicity. The WHO suggests lower BMI cutoffs for Asian populations (overweight at 23, obese at 27.5) due to higher metabolic risk at lower body weights. Conversely, some Pacific Islander and African populations may have lower health risks at slightly higher BMI levels. Context matters when interpreting your result.