2026 BMI Calculator

BMI = weight (kg) ÷ height (m)². In imperial units, the formula is BMI = [weight (lb) ÷ height (in)²] × 703. For example, a person who is 5'9" (69 inches) and weighs 170 lb would calculate: (170 ÷ 69²) × 703 = 25.1. This formula was developed by Belgian statistician Adolphe Quetelet in the 1830s and adopted by the WHO in 1995 as the international standard for adult weight classification. The CDC uses the same formula for all adults aged 20 and older, regardless of sex or ethnicity. The 703 multiplier in the imperial formula converts the result to match the metric-based kg/m² scale. You can verify your calculation using the calculator above, which handles unit conversion automatically.

The CDC and WHO define normal weight as a BMI between 18.5 and 24.9. Below 18.5 is classified as underweight, 25.0–29.9 is overweight, and 30.0 or higher is obese. For a 5'9" adult, this healthy range translates to approximately 126–169 lb. The midpoint of the normal range is roughly BMI 21.7, which many clinicians consider the "ideal" target. Research published in the New England Journal of Medicine shows that all-cause mortality risk is lowest in the BMI 20–25 range and increases by approximately 31% per 5-unit BMI increase above 25. For adults over 65, some studies suggest a slightly higher range of 23–28 may be optimal (see the age-adjusted table above). The CDC recommends regular BMI screening at annual wellness visits.

Yes, BMI can be misleading at the individual level because it does not differentiate muscle from fat. Athletes with high muscle mass — such as NFL linebackers, CrossFit competitors, or bodybuilders — may have a BMI over 25 or even 30 while carrying only 10–15% body fat, well within the healthy range. A 2016 UCLA study found that over 54 million Americans classified as "overweight" or "obese" by BMI were actually metabolically healthy. Conversely, "normal-weight obesity" (also called "skinny fat") affects an estimated 30% of people with normal BMIs who carry excess body fat above 25% (men) or 32% (women). For a more accurate assessment, combine BMI with body fat percentage and waist circumference measurements. The NIH recommends all three metrics together for clinical assessment.

The CDC uses the same BMI thresholds for men and women — normal weight is 18.5–24.9 for both sexes. However, women naturally carry 6–11% more body fat than men at the same BMI due to physiological differences in fat distribution (breasts, hips, thighs). At a BMI of 24, a typical woman has approximately 30% body fat while a man averages about 20%. This means a woman at the upper end of "normal" BMI may already have elevated metabolic risk compared to a man at the same BMI. The American Council on Exercise defines healthy body fat ranges as 14–24% for men and 21–31% for women. For this reason, the NIH recommends using body fat percentage alongside BMI, especially for women approaching the overweight threshold.

A BMI of 30.0 or higher is classified as obese by the CDC, which further divides obesity into three classes: Class 1 (BMI 30.0–34.9), Class 2 (BMI 35.0–39.9), and Class 3 or severe obesity (BMI 40.0 and above). According to NHANES 2022–2024 data, 41.9% of U.S. adults have a BMI of 30 or higher, and 9.2% have severe obesity (BMI 40+). Health risks escalate dramatically with each class: adults with a BMI of 30–35 are 3–7 times more likely to develop Type 2 diabetes compared to those with a normal BMI of 18.5–24.9 (CDC). Class 2 obesity (BMI 35+) doubles the risk of heart failure, while Class 3 obesity (BMI 40+) reduces average life expectancy by 8–14 years according to NIH research. The annual medical cost difference between an obese adult and a healthy-weight adult averages $1,861. For BMI 40+, bariatric surgery may be clinically recommended by the NIH.

No — the standard adult BMI thresholds of 18.5, 25.0, and 30.0 do not apply to anyone under age 20. Children and teens use BMI-for-age percentiles, which compare a child's BMI against age- and sex-specific growth charts maintained by the CDC. A child at the 85th–94th percentile is classified as overweight, while the 95th percentile and above is classified as obese. According to CDC NHANES 2019–2020 data, 19.7% of U.S. children aged 2–19 have obesity (BMI at or above the 95th percentile), affecting approximately 14.7 million children. For children aged 2–5, the obesity rate is 12.7%; for ages 6–11, it is 20.7%; and for ages 12–19, it is 22.2%. Pediatric BMI percentiles are essential because body fat levels change naturally during growth. This calculator is designed specifically for adults aged 20 and older. For children, the CDC provides a separate BMI Percentile Calculator.

Yes — the WHO Asia-Pacific guidelines define lower BMI thresholds for people of Asian descent: overweight starts at 23.0 (not 25.0) and obese starts at 25.0 (not 30.0). Research published in The Lancet and by the WHO Expert Consultation found that Asian populations develop Type 2 diabetes, hypertension, and cardiovascular disease at significantly lower BMIs than European-descent populations. An Asian American with a BMI of 24 faces metabolic risk comparable to a European American with a BMI of 28-29. Approximately 24 million Asian Americans (7.2% of the US population) may benefit from these adjusted thresholds. The CDC currently uses the same 25/30 cutoffs for all races, but the American Diabetes Association (ADA) recommends diabetes screening for Asian Americans starting at BMI 23 rather than the standard 25. If you are of Asian descent, discuss these lower thresholds with your healthcare provider.

Life insurance companies use BMI as a primary factor in underwriting risk classification. Most insurers assign "rate classes" that directly determine your monthly premium. A Preferred Plus rate (BMI 18.5–25) can save 30–50% compared to a Standard rate (BMI 30–35). Typical annual premium differences for a 35-year-old seeking $500,000 in 20-year term coverage: BMI 22 (Preferred Plus) ~$320/year, BMI 27 (Preferred) ~$420/year, BMI 32 (Standard) ~$580/year, BMI 37 (Substandard) ~$900+/year. Most insurers decline coverage or charge Table-rated premiums above BMI 40-45. Importantly, insurers use your measured height and weight (from a paramedical exam), not self-reported figures. A BMI reduction from 31 to 24.9 could save $260+/year in premiums — over a 20-year term, that's $5,200+ in savings.

A BMI between 25.0 and 29.9 classifies you as overweight, but this is a screening result, not a medical diagnosis. The NIH and CDC recommend these clinical next steps: (1) Measure your waist circumference — men over 40 inches (102 cm) and women over 35 inches (88 cm) face elevated metabolic risk even at the lower end of overweight. (2) Assess comorbidities: high blood pressure (≥130/80 mmHg), elevated fasting glucose (≥100 mg/dL), high LDL cholesterol (≥160 mg/dL), or family history of cardiovascular disease. (3) If waist circumference OR two+ risk factors are present, the NHLBI guidelines recommend a structured weight reduction program targeting 1–2 lb/week through a 500–1,000 calorie/day deficit. (4) Schedule a wellness visit with your primary care provider for a complete metabolic panel. Approximately 72% of overweight adults have at least one additional cardiovascular risk factor (NHANES data). The financial impact matters too: overweight adults pay an average of $1,125 more per year in medical costs (CDC).

The CDC recommends BMI screening at every annual wellness visit for adults, but meaningful tracking depends on your health situation. For general health maintenance with a normal BMI (18.5–24.9), annual checks are sufficient — body composition changes slowly in most adults. If you're actively losing or gaining weight, weekly weigh-ins with monthly BMI calculations provide better trend data without daily noise (body weight fluctuates 2–4 lb daily from water, food, and sodium). For post-bariatric surgery patients, the ASMBS recommends monthly BMI tracking for the first year, then quarterly. Seasonal patterns are real: NEJM research shows Americans gain an average of 1.3 lb during the November–January holiday period, accounting for roughly 50% of annual weight gain. The best practice is to weigh yourself at the same time (morning, post-bathroom, pre-breakfast) on the same scale. Our BMI calculator stores no data — you may want to log results in a health app for trend tracking.

In June 2023, the American Medical Association (AMA) adopted Policy H-440.842, stating that BMI is an "imperfect measure" that should not be used as the sole criterion for denying medical treatment or insurance coverage. The AMA cited several limitations: BMI was originally developed for population-level statistics (not individual diagnosis), it does not account for differences in body composition, bone density, sex, race, or ethnicity, and its historical roots in data from predominantly white European populations create bias against other groups. The AMA recommended using BMI in conjunction with visceral fat measurement, body adiposity index (BAI), waist circumference, and metabolic biomarkers (blood glucose, lipids, blood pressure). Notably, the AMA did not recommend abandoning BMI — rather, it advocated for multi-metric assessment. The policy was prompted partly by research showing that approximately 54 million Americans classified as "overweight" or "obese" by BMI alone are metabolically healthy, while 6% of "normal-weight" individuals have metabolic syndrome. For practical purposes, BMI remains the most accessible free screening tool — the key is not relying on it exclusively.