Enter your height in centimeters or feet and inches, plus your weight in kilograms, to get your BMI and category instantly.
US Navy method — needs a tape measure, not just a scale.
BMI is weight in kilograms divided by height in meters squared: BMI = kg ÷ m². Enter weight in pounds and it's converted automatically (÷2.20462), and height in feet & inches converts to meters the same way — the underlying formula is identical worldwide, only the input units change between the US customary system and the metric system used almost everywhere else.
No. BMI is a screening estimate based on height and weight only — it says nothing directly about body fat percentage, muscle mass, bone density, or where fat is distributed, all of which affect health risk independently of the number on this scale. The World Health Organization and most national health bodies (US CDC, UK NHS, and India's ICMR) use it as a population-level screening tool, not an individual diagnostic one. Treat the category below as a conversation starter with a doctor, not a verdict.
BMI Prime is your BMI divided by the upper healthy threshold (25): a value of exactly 1.0 sits right at the boundary between healthy and overweight, values under 1.0 are in or below the healthy range, and values over 1.0 tell you, as a simple ratio, how far above that boundary you are — 1.2 means roughly 20% above the healthy-weight ceiling. It's a small addition, but it makes cross-comparisons (tracking change over time, or comparing two people of different heights) more intuitive than raw BMI alone.
Under 18.5 is underweight, 18.5–24.9 is the healthy range, 25–29.9 is overweight, and 30+ is obese — obesity is further split clinically into Class I (30–34.9), Class II (35–39.9), and Class III (40+). These WHO thresholds are used as the default across the US, UK, and most of Europe. Several Asian health authorities, including India's and the wider WHO Asia-Pacific guidance, use lower cut-offs (23 for overweight, 25 for obese) because cardiovascular and diabetes risk tends to rise at lower BMI values in South and East Asian populations. Switch the "BMI standard" toggle above to Asia-Pacific to apply these lower cut-offs directly, rather than mentally adjusting the standard result.
Rearranging the BMI formula for weight at the boundaries of the healthy range (18.5 and 24.9) gives the healthy weight range shown above — for a 175cm adult, that's roughly 56.7–76.3 kg. It's a wide range on purpose: BMI alone can't pin down an ideal weight for an individual, only a broad healthy band. If you'd rather target one specific number, formulas like Devine or Robinson (used clinically for drug dosing, not general health) exist, but for everyday purposes the BMI-derived range above is the more honest answer.
No — BMI for anyone under 20 is interpreted using age- and sex-specific percentile charts (CDC growth charts in the US, UK-WHO charts in the UK, IAP charts in India), not the fixed adult categories this calculator uses, because healthy body composition changes substantially through growth. A pediatrician's growth chart is the correct tool for a child or teen, not this page.
No — BMI can't distinguish muscle from fat, so a muscular person can register as "overweight" or even "obese" despite low body fat, because muscle is denser than fat tissue. Body fat percentage, waist-to-height ratio, or a DEXA scan are more accurate for that specific case. As a quick sanity check outside this calculator: waist circumference under half your height is a reasonable sign that a high BMI is more likely muscle than visceral fat.
Quetelet's original 19th-century formula used height squared because it happened to correlate reasonably well with body fat across an average adult population — it's a statistical convenience, not a physical law. This is also why BMI systematically over-estimates fatness in very tall people and under-estimates it in very short people; researchers have proposed alternatives (like the "New BMI" using height^2.5) to correct this, but the classic squared formula remains the global standard because of how deeply embedded it is in clinical guidelines and research.
The formula and the classic 18.5/25/30 thresholds are identical in the US, UK, and EU. India (and the WHO Asia-Pacific standard) uses the lower 23/25 cut-offs described above, reflecting population-level research on cardiometabolic risk — use the toggle above to switch between them instantly. If you're using this tool for a general check rather than clinical purposes, the difference mainly matters near the 23–25 boundary — someone reading "healthy" under the standard scale could be flagged "overweight" under the Asia-Pacific one.
Worked example: a person 175 cm tall weighing 72 kg has a BMI of 72 ÷ (1.75×1.75) = 72 ÷ 3.0625 ≈ 23.5 — healthy range under WHO standard thresholds, but at the edge of "overweight" under the Asia-Pacific 23-cut-off. Their BMI Prime is 23.5 ÷ 25 ≈ 0.94, and their healthy weight range at that height is roughly 56.7–76.3 kg.
The Devine formula gives a single "ideal weight" number (50 kg + 2.3 kg per inch over 5 feet for men, 45.5 kg + 2.3 kg per inch for women) — it was originally developed for drug dosing calculations, not general health guidance, which is why it lands on one specific number rather than the wider healthy range BMI produces. Treat it as a clinical reference point, not a personal target.
The US Navy method estimates body fat from neck, waist, and (for women) hip circumference plus height, using a logarithmic formula validated against more expensive methods like DEXA scans. It's more informative than BMI alone since it separates fat from muscle, but a tape measure introduces its own error — measure at the same time of day, without clothing compression, for consistent tracking over time.
Curious about the medical side of weight management? See what WHO's new GLP-1 obesity guideline actually says — an explainer, not medical advice. Wondering what treatment actually costs? See what GLP-1 drugs cost in the US, UK, India, and EU in 2026. Overall wellness also means sleep — try the Sleep Cycle Calculator. Need your height or weight in different units first? Try the CM to Inches and KG to Pounds converters. BMI ignores body composition entirely — for a measurement-based estimate see the Army Body Fat Calculator, which uses the tape-test method. For children rather than adults, BMI is read against age-and-sex percentiles rather than fixed cut-offs — and if the question is future height, the Child Height Predictor gives the mid-parental range. Other clinical measures of body size and function: the Body Surface Area Calculator and the eGFR Calculator.