BMI Calculator

BMI (Body Mass Index) is the world's most widely used screening tool for weight category, with over 4 million Americans searching for a BMI calculator every month. This calculator gives you your BMI, CDC weight category, ideal weight range for your height, BMR, and TDEE — the complete picture health professionals use to assess weight-related health risk. **Enter your height and weight** Use either imperial (feet/inches, pounds) or metric (centimeters, kilograms). Double-check your inputs: a 1-inch height error shifts BMI by roughly 0.5 points, which can change your category at the boundary. For the most accurate result, measure your height without shoes and your weight in the morning before eating. **Understanding your BMI result** The CDC defines four weight categories for adults 20 and older: - Underweight: BMI below 18.5 - Normal weight: BMI 18.5–24.9 - Overweight: BMI 25.0–29.9 - Obese: BMI 30.0 and above Obesity is further subdivided: Class 1 (BMI 30–34.9), Class 2 (35–39.9), Class 3 or severe obesity (40+). **Ideal Weight by Height: The Complete Reference Table** This table shows the healthy weight range (BMI 18.5–24.9) for adults of every height. The formula used is the standard BMI calculation: weight (lbs) = BMI × [height (inches)]² / 703. Height | Healthy Weight Range | Overweight starts | Obese starts 4'10" (58") | 91–119 lbs | 119 lbs | 143 lbs 4'11" (59") | 94–123 lbs | 124 lbs | 148 lbs 5'0" (60") | 97–127 lbs | 128 lbs | 153 lbs 5'1" (61") | 100–132 lbs | 132 lbs | 158 lbs 5'2" (62") | 104–136 lbs | 136 lbs | 164 lbs 5'3" (63") | 107–140 lbs | 141 lbs | 169 lbs 5'4" (64") | 110–144 lbs | 145 lbs | 174 lbs 5'5" (65") | 114–149 lbs | 150 lbs | 180 lbs 5'6" (66") | 118–154 lbs | 155 lbs | 186 lbs 5'7" (67") | 121–158 lbs | 159 lbs | 191 lbs 5'8" (68") | 125–163 lbs | 164 lbs | 197 lbs 5'9" (69") | 128–168 lbs | 169 lbs | 203 lbs 5'10" (70") | 132–173 lbs | 174 lbs | 209 lbs 5'11" (71") | 136–178 lbs | 179 lbs | 215 lbs 6'0" (72") | 140–183 lbs | 184 lbs | 221 lbs 6'1" (73") | 144–188 lbs | 189 lbs | 227 lbs 6'2" (74") | 148–194 lbs | 195 lbs | 233 lbs 6'3" (75") | 152–199 lbs | 200 lbs | 240 lbs 6'4" (76") | 156–204 lbs | 205 lbs | 246 lbs 6'5" (77") | 160–210 lbs | 211 lbs | 253 lbs 6'6" (78") | 164–215 lbs | 216 lbs | 259 lbs **What Is a Healthy BMI for a Woman?** The CDC defines healthy weight as BMI 18.5–24.9 for all adults regardless of sex. For a 5'4" woman, that is 110–144 pounds. For a 5'6" woman, that is 118–154 pounds. However, important nuances apply specifically to women: - Women naturally carry 5–10% more body fat than men at the same BMI due to hormonal and reproductive differences. This is physiologically normal and does not increase health risk. - Pregnant women: BMI calculations are not appropriate during pregnancy. The CDC and ACOG use separate gestational weight gain guidelines based on pre-pregnancy BMI. - Postmenopausal women: After menopause, fat often redistributes to the abdomen. A BMI of 22–24 with high waist circumference can carry elevated metabolic risk even within the healthy BMI range. - Asian women: The AHA recommends lower thresholds — overweight at BMI 23+. At BMI 25, Asian women carry significantly more body fat and higher metabolic disease risk than white European women at the same BMI. **BMI Chart by Age: How Health Risks Shift** The standard BMI thresholds (underweight, normal, overweight, obese) do NOT change with age for adults 20 and older. A BMI of 27 is classified as overweight whether you are 25 or 75. However, the health implications of BMI change significantly with age: Age 20–40: Standard CDC thresholds apply. Overweight BMI (25–29.9) significantly increases long-term risk of type 2 diabetes, cardiovascular disease, and certain cancers. Age 40–65: The metabolic consequences of overweight BMI intensify. Risk of hypertension, fatty liver disease, and sleep apnea increases. Even modest weight loss (5–10%) produces measurable improvements in blood pressure and blood glucose. Age 65+: Counterintuitively, research published in the American Journal of Clinical Nutrition suggests that a slightly higher BMI (23–27) may be protective for older adults. Excess weight provides a reserve against the frailty and muscle wasting (sarcopenia) that accelerates in aging. For adults over 70, a BMI below 22 is associated with higher mortality than a BMI of 25–27. **Children's BMI: Completely Different Rules** For anyone under 20 years old, adult BMI thresholds do not apply. Children's BMI is interpreted using age-specific and sex-specific CDC growth charts as BMI-for-age percentile. CDC BMI-for-age categories: - Below 5th percentile: Underweight - 5th–84th percentile: Healthy weight - 85th–94th percentile: Overweight - 95th percentile and above: Obesity Why percentiles instead of fixed numbers? A 10-year-old boy and a 16-year-old boy with the same height and weight have very different body composition. The same BMI number (e.g., 22) is severe obesity for a 10-year-old and perfectly healthy for a 17-year-old. This is why the CDC maintains separate growth charts and why pediatricians track BMI percentile at every well-child visit. For children, use the CDC's dedicated BMI-for-Age calculator at cdc.gov — it accounts for age in years and months and compares to the reference population. Never use adult BMI categories for anyone under 20. **Obesity Health Risks: What the Numbers Actually Mean** BMI is not just a number — each class of obesity is associated with specific, quantified health risks supported by decades of epidemiological research: Overweight (BMI 25–29.9): - 1.3x increased risk of type 2 diabetes - 1.2x increased risk of coronary artery disease - Increased risk of sleep apnea, gallstones, and certain cancers Class 1 Obesity (BMI 30–34.9): - 2x increased risk of type 2 diabetes (vs. healthy weight) - 1.5x increased risk of heart disease - Significant risk of hypertension (high blood pressure affects 70% of obese adults) Class 2 Obesity (BMI 35–39.9): - 3x increased risk of type 2 diabetes - Severe sleep apnea risk: 77% of morbidly obese patients have clinically significant sleep-disordered breathing - Knee osteoarthritis: every pound of body weight adds 4 pounds of pressure to the knee joint Class 3 (Severe) Obesity (BMI 40+): - 10x increased risk of type 2 diabetes compared to normal weight - 3x increased risk of coronary artery disease - Dramatically reduced life expectancy: severe obesity at age 40 is associated with 6–14 years of lost life expectancy depending on sex and race - Bariatric surgery becomes the most effective treatment option — lifestyle interventions rarely achieve sustained weight loss above BMI 40 Source: National Institutes of Health (NIH), CDC, and the American Heart Association clinical guidelines. **BMI History and Why the AMA Changed Its Position** BMI was invented by Adolphe Quetelet, a Belgian mathematician, in the 1830s for population statistics — not individual medical assessment. Insurance companies adopted it in the 1900s to set premiums, and the WHO and CDC formalized its clinical use in the late 20th century. In June 2023, the American Medical Association passed a landmark policy acknowledging BMI's limitations and explicitly stating it should not be used as the sole diagnostic criterion. The AMA cited three specific problems: the formula was derived from predominantly non-Hispanic white populations, it cannot distinguish muscle from fat, and it does not account for body fat distribution. **BMI vs. Body Fat Percentage: A Direct Comparison** Method | Accuracy | Cost | Notes BMI | Low-moderate | Free | Cannot distinguish fat from muscle Skin-fold calipers | Moderate | $15–30 | Requires trained assessor Bioelectrical impedance (scale) | Moderate | $30–200 | Affected by hydration level Hydrostatic weighing | High | $50–100/session | Gold standard for decades DEXA scan | Very high | $100–300/scan | Best clinical option available MRI body composition | Highest | $1,000+ | Research/academic settings only For the most practical improvement over BMI at zero additional cost: measure your waist circumference. Abdominal fat (visceral fat) is more strongly linked to metabolic disease than total body fat. Risk thresholds: women above 35 inches = elevated risk; men above 40 inches = elevated risk — regardless of what your BMI says. **The Mifflin-St Jeor BMR Formula: Step-by-Step** Basal Metabolic Rate (BMR) is the calories your body burns at complete rest. The Mifflin-St Jeor equation is the most validated for non-athlete adults: Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5 Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161 Example: 35-year-old woman, 145 lbs (65.8 kg), 5'5" (165.1 cm) Step 1: 10 × 65.8 = 658 Step 2: 6.25 × 165.1 = 1,032 Step 3: 5 × 35 = 175 Step 4: 658 + 1,032 − 175 − 161 = 1,354 calories/day BMR Multiply BMR by your activity factor to get TDEE: sedentary (1.2), lightly active (1.375), moderately active (1.55), very active (1.725). For this example at moderately active: 1,354 × 1.55 = 2,099 calories/day to maintain weight. **BMI by Ethnicity: Adjusted Thresholds** Standard BMI thresholds were developed using predominantly white European populations. Research shows health risks occur at different BMI levels across ethnic groups: Asian populations (Chinese, Japanese, Korean, South Asian): Overweight at BMI 23+, obese at BMI 27.5+. At BMI 25, Asian individuals carry approximately 3–5% more body fat than white European individuals. Black populations: Research suggests Black adults may have lower body fat at the same BMI, meaning standard thresholds may overestimate health risk. Some research supports higher thresholds for overweight classification. Hispanic populations: Higher cardiovascular risk at lower BMI levels compared to non-Hispanic white populations, but less extreme than Asian adjustment thresholds. **Common BMI Misinterpretations** 1. Treating a single BMI reading as a health diagnosis: BMI is a screening tool, not a diagnosis. It identifies who needs further evaluation. 2. Ignoring trend: BMI rising from 24 to 28 over five years is more clinically significant than a stable 28. 3. Applying adult thresholds to children: This produces wildly incorrect assessments. Always use age-specific percentile charts for anyone under 20. 4. Assuming normal BMI equals metabolically healthy: Normal weight obesity affects an estimated 30 million Americans. 5. Using BMI alone for athletes: Muscular athletes routinely show BMI 26–32 with under 15% body fat.