Calculate your Body Mass Index and healthy weight range
Body Mass Index (BMI) is a measure of body fat based on height and weight that applies to adult men and women. BMI is an inexpensive and easy screening method for weight category.
BMI Prime is a modification of the BMI system. A BMI Prime of 1.0 is at the upper limit of normal weight. Values below 0.74 are underweight, and values above 1.0 are overweight.
Yes and no. BMI remains a useful population-level screening tool because it's free, quick, and correlates with health risks for most people. However, modern research shows BMI alone misclassifies health status in 30-40% of individuals. A 2023 study in The Lancet found that combining BMI with waist-to-height ratio improves health risk prediction by 25%. Bottom line: Use BMI as a starting point, but don't let it be your only metric. If your BMI is 'overweight' but your waist circumference is healthy and you're metabolically fit (good blood pressure, blood sugar, cholesterol), you're likely fine.
BMI cannot distinguish between fat mass and lean mass. Muscle is denser than fat - one pound of muscle occupies about 18% less space than one pound of fat. This is why bodybuilders, athletes, and people who lift weights often have 'overweight' or 'obese' BMIs despite low body fat percentages. Example: At 5'10" and 200 lbs, a sedentary person with 30% body fat (60 lbs fat) would have the same BMI (28.7, 'overweight') as a muscular athlete with 10% body fat (20 lbs fat). The solution? Add body composition metrics: waist circumference, body fat percentage, or waist-to-height ratio.
Absolutely. The WHO's 18.5-25 range was derived primarily from Caucasian populations. Research shows Asian populations face increased health risks at lower BMIs. For example, individuals of South Asian, Chinese, and Japanese descent show elevated diabetes and cardiovascular risk at BMI 23-24, not 25. Conversely, Pacific Islanders and some Black populations can be healthy at slightly higher BMIs due to different body compositions. WHO now recommends for Asian adults: overweight at BMI ≥23, obese at BMI ≥27.5. Always consider ethnicity-specific guidelines alongside standard BMI ranges.
Yes. BMI becomes less reliable after age 65 due to age-related muscle loss (sarcopenia). Older adults lose approximately 3-8% of muscle mass per decade after 30, accelerating after 60. This means a 70-year-old with 'normal' BMI (22) might actually have high body fat and low muscle mass - a condition called 'sarcopenic obesity' that increases fall risk, frailty, and mortality. Paradoxically, research shows slightly higher BMIs (25-27) may be protective in older adults - the 'obesity paradox.' For seniors, waist circumference, grip strength, and functional fitness are better health indicators than BMI alone.
Large meta-analyses show a J-shaped mortality curve. Lowest all-cause mortality occurs at BMI 22-25 for non-smokers. However, the 'healthiest' BMI depends on factors like fitness level and where you carry fat. A 2016 study of 3.6 million people found: BMI 18.5-22 is ideal IF you're physically active and don't smoke; BMI 22-25 shows no increased mortality for most people; BMI 27-30 ('overweight') only increases mortality risk if combined with metabolic issues (high blood pressure, diabetes, etc.). Interestingly, fit individuals with BMI 27-29 have lower mortality than unfit individuals with BMI 22-24. This suggests cardiorespiratory fitness trumps BMI for longevity.
Significantly more important. Visceral fat (deep abdominal fat around organs) is metabolically active and inflammatory - it releases hormones that increase diabetes, heart disease, and cancer risk. Subcutaneous fat (under the skin, like hip/thigh fat) is relatively benign. Two people with identical BMI 28 can have vastly different health: Person A: waist circumference 40 inches (visceral fat) - high risk. Person B: waist circumference 32 inches (subcutaneous fat in hips/thighs) - low risk. Waist-to-height ratio is a better predictor: keep your waist circumference less than half your height. For a 5'8" person (68 inches), that's under 34 inches regardless of BMI.
Yes - it's called 'metabolically healthy obesity' (MHO), affecting about 10-30% of people with obese BMIs. These individuals have: normal blood pressure (<130/85), normal fasting glucose (<100 mg/dL), normal triglycerides (<150 mg/dL), healthy HDL cholesterol (>40 men, >50 women), and low inflammation markers. However, long-term studies show MHO is often temporary - 30-50% transition to metabolically unhealthy within 10 years. Protective factors include: regular exercise (150+ min/week), maintaining muscle mass, carrying weight in hips/thighs not abdomen, and not smoking. Bottom line: You can be healthier than your BMI suggests, but obesity still carries long-term risks even without current metabolic issues.
Hormones profoundly influence where and how you store fat, independent of calories. Key players: (1) Insulin: High insulin (from frequent eating, processed carbs) promotes fat storage, especially visceral fat. (2) Cortisol: Chronic stress elevates cortisol, which increases appetite and belly fat accumulation. (3) Estrogen: Declining estrogen during menopause shifts fat from hips/thighs to abdomen, increasing health risks even if BMI stays constant. (4) Testosterone: Low testosterone in men (and women) reduces muscle mass and increases fat, worsening body composition at the same BMI. (5) Thyroid: Hypothyroidism can slow metabolism by 20-40%, making weight gain easy even with modest calorie intake. If your BMI is increasing despite lifestyle efforts, check: fasting insulin, cortisol, sex hormones, and thyroid function (TSH, free T3).
Body fat percentage is more informative but harder to measure accurately. Healthy ranges: Men 10-20%, Women 18-28% (athletes lower, essential fat 3-5% men, 8-12% women). The problem: accurate measurement requires DEXA scans or hydrostatic weighing. Home scales using bioelectrical impedance can be off by 5-8%. BMI's advantage is it requires only height and weight - accessible to everyone. Best approach: Track multiple metrics together. Example for a 5'6" woman: BMI 24 (normal) + body fat 32% (high) + waist 35" (high) = health risk despite 'normal' BMI. BMI 27 (overweight) + body fat 24% (healthy) + waist 29" (healthy) = likely metabolically healthy. If you can only track one thing, waist-to-height ratio beats BMI for health prediction.
Athletes should largely ignore BMI and focus on performance metrics and body composition. Examples: Rugby players, NFL linebackers: Often BMI 30-35 ('obese') but 8-15% body fat. Endurance runners: Often BMI 18-20 ('underweight') but healthy for their sport. Gymnasts, dancers: BMI 17-19 but high muscle mass and low body fat. Better metrics for athletes: (1) Body fat percentage: 6-13% men, 14-20% women for most sports. (2) Lean body mass: Track muscle mass, not just weight. (3) Performance markers: Power output, VO2 max, strength ratios. (4) Recovery metrics: HRV, sleep quality, injury frequency. (5) Functional movement: Mobility, stability, sport-specific skills. The only time athletes should monitor BMI is for weight-class sports (wrestling, boxing) where it affects competition category - but even then, body composition matters more than the number.
Absolutely. BMI obsession can fuel disordered eating, body dysmorphia, and mental health issues. Research shows that weight stigma and BMI-based discrimination cause psychological harm and paradoxically worsen health outcomes. Problems with BMI fixation: (1) It ignores health behaviors - a 'normal' BMI person who smokes, is sedentary, and eats poorly is less healthy than an 'overweight' person who exercises regularly and eats well. (2) It can trigger restrictive eating or over-exercise, especially in adolescents. (3) It reduces health to a single number, ignoring sleep, stress, relationships, and mental wellbeing. (4) BMI-based shame increases cortisol, which ironically promotes fat storage. Better approach: Focus on health-promoting behaviors rather than numbers. Ask: Am I eating mostly whole foods? Am I moving daily? Is my sleep quality good? Are my energy levels stable? Do I feel strong? These matter more than hitting a BMI target.
Use a combination of metrics that capture different aspects of health: (1) Waist-to-Height Ratio: Measure waist at belly button level. Divide by height. Target: <0.5 for both sexes. Example: 32-inch waist ÷ 68 inches tall = 0.47 (excellent). This predicts cardiovascular risk better than BMI. (2) Body Composition: If accessible, get DEXA scan every 6-12 months tracking fat mass, lean mass, visceral fat, and bone density. (3) Metabolic Markers: Annual bloodwork - fasting glucose, HbA1c, lipid panel, hs-CRP (inflammation), liver enzymes. These show internal health regardless of weight. (4) Functional Fitness: Can you do 10 push-ups? Touch your toes? Carry groceries upstairs without breathlessness? Functional capacity predicts longevity. (5) Resting Heart Rate & Blood Pressure: Lower is generally better (RHR 50-70, BP <120/80). Track these weekly. (6) How clothes fit: More practical than daily weighing. If your pants fit the same over 6 months, your body composition is stable. Together, these paint a complete health picture BMI alone cannot provide.