BMI Calculator
Assess your body mass index and healthy range.
How to use: Enter your age, gender, height, and weight to see your Body Mass Index (BMI) and recommended healthy weight range.
Anthropometric Diagnostic Suite
BMI Calculator: Calculate Your Body Mass Index
ZA
Reviewed by Dr. Zohaib Ali
Last updated April 2026
What is BMI, and how is it calculated?
Quick Answer: BMI (Body Mass Index) = weight (kg) ÷ height (m)². In US customary units: BMI = [weight (lbs) ÷ height (inches)²] × 703.
WHO adult categories: Underweight = below 18.5 | Normal weight = 18.5–24.9 | Overweight = 25–29.9 | Obese = 30+.
Note: For adults of Asian descent, WHO recommends a lower overweight threshold of 23 (not 25). BMI is a screening tool, not a diagnosis. The American Medical Association’s 2023 policy states BMI should not be used as a sole clinical measure of health.
Medical Disclaimer
Important: This calculator is a screening tool for educational purposes only. BMI does not measure body fat percentage, account for muscle mass, or assess body composition. It is not a substitute for professional medical evaluation. If you have concerns about your weight or health, speak with a physician or registered dietitian. This tool is not intended for use by individuals with or recovering from eating disorders.
Clinical References: World Health Organization (WHO); CDC; American Medical Association (AMA) 2023 Policy.
What BMI Is And What It Was Never Designed to Do
Body Mass Index is a number calculated from your height and weight. It divides your weight in kilograms by your height in meters squared. The result places you into one of four categories: underweight, normal weight, overweight, or obese. It takes 30 seconds to calculate. It requires no equipment. It’s been used in clinical medicine and public health research for over 50 years.
It’s also acknowledged by the acknowledgment of every major medical body, including the AMA, the WHO, and the CDC, as an imperfect, incomplete, and systematically biased tool when used as a sole indicator of an individual’s health.
Understanding both things simultaneously is the honest approach: BMI is a useful population-level screening tool that helps identify weight categories associated with increased health risk at a group level. It is not a diagnosis. It does not measure body fat directly. It was not designed for individual clinical assessment. And since June 2023, the American Medical Association has explicitly stated it should not be used as such.
Enter your height and weight above for your BMI result and read the sections below to understand exactly what the number does and doesn’t tell you.
The BMI Formula: Both Metric and US Units
Metric (kilograms and meters)
BMI = weight (kg) ÷ height (m)²
Example: 70 kg ÷ (1.75 m)² = 70 ÷ 3.0625 = BMI 22.9
US customary (pounds and inches)
BMI = [weight (lbs) ÷ height (inches)²] × 703
Example: 154 lbs ÷ (69 inches)² × 703 = 154 ÷ 4,761 × 703 = BMI 22.7
The calculator above handles all unit conversions automatically. No manual calculation required.
WHO BMI Categories for Adults (Age 20 and Older)
These are the World Health Organization’s standard adult BMI classifications, used by the CDC and most US healthcare providers:
| BMI | Category | Health Risk Indication |
|---|---|---|
| Below 18.5 | Underweight | Possible malnutrition, bone loss, immune deficiency |
| 18.5 – 24.9 | Normal / Healthy weight | Lowest population-level disease risk |
| 25.0 – 29.9 | Overweight | Increased risk for cardiovascular disease, type 2 diabetes |
| 30.0 – 34.9 | Obese — Class I | Moderate increased risk |
| 35.0 – 39.9 | Obese — Class II | High increased risk |
| 40.0 and above | Obese — Class III | Very high increased risk |
Important context:These thresholds are based primarily on research conducted on White European populations. They are population-level categories, not individual diagnoses. A BMI of 26 does not mean a specific person has poor health. It means people with that BMI, on average, have slightly elevated rates of certain conditions compared to people in the 18.5–24.9 range.
The AMA’s 2023 Position: Why BMI’s Clinical Role Changed
In June 2023, the American Medical Association adopted a formal policy statement that represents the most significant institutional shift in BMI’s clinical standing in decades. The key points:
1. BMI has racist origins
Adolphe Quetelet, a Belgian mathematician (not a physician), developed the formula in the 1830s using data exclusively from White European men. Ancel Keys renamed it “Body Mass Index” in 1972. Neither creator designed it for individual clinical use, and neither collected data on diverse populations.
2. BMI perpetuates bias
Research confirms BMI performs differently across racial and ethnic groups. It systematically overestimates body fat in Black Americans at the same BMI as White Americans (Journal of the Endocrine Society, 2024). It underestimates health risk in Asian Americans who face significant metabolic risk at BMIs that would classify as “normal weight” under standard thresholds.
3. BMI should be supplemented
The AMA’s 2023 policy recommends using BMI alongside waist circumference, waist-to-height ratio, body composition measurements, and direct measures of visceral fat for individual clinical assessment.
What this means for you:Your BMI number is one data point, and it’s a useful one for understanding where you fall relative to population-level risk categories. It is not a verdict on your health, fitness, or body composition. Use it as a starting point, not a destination.
Ethnicity-Adjusted BMI Thresholds: The Table Nobody Shows You
The standard WHO thresholds (overweight at 25, obese at 30) were validated primarily on European populations. For certain ethnic groups, these thresholds under- or over-predict health risk. Here are the adjusted recommendations currently in clinical use:
| Population | Standard Overweight | Adjusted Overweight | Standard Obese | Adjusted Obese |
|---|---|---|---|---|
| White / European | ≥25.0 | Same | ≥30.0 | Same |
| East Asian, South Asian, Southeast Asian | ≥25.0 | ≥23.0 | ≥30.0 | ≥27.5 |
| South Asian (India, Pakistan, Bangladesh) | ≥25.0 | ≥23.0 | ≥30.0 | ≥25.0 (some guidelines) |
| Black / African American | ≥25.0 | Research suggests higher threshold? | ≥30.0 | Under active research |
| Polynesian / Pacific Islander | ≥25.0 | Evidence supports higher thresholds | ≥30.0 | Debated |
Why Asian adults use lower thresholds:At the same BMI as European adults, Asian adults carry significantly more visceral fat (fat around abdominal organs) and carry a higher metabolic risk, specifically for type 2 diabetes and cardiovascular disease. The WHO’s 2004 Asia-Pacific guideline, endorsed by clinical organizations including the American Diabetes Association, recommends screening Asian American adults for type 2 diabetes at a BMI ≥23.
The practical implication:If you are of South Asian, East Asian, or Southeast Asian descent, standard BMI thresholds underestimate your cardiometabolic risk. Discuss adjusted thresholds and waist circumference measurements with your physician.
The Number That Puts Your BMI in Context: Your US Percentile
The average adult BMI in the United States is approximately 28–29, according to CDC NHANES (National Health and Nutrition Examination Survey) data. Obesity class I (BMI 30–35) affects approximately 32% of US adults. The majority of American adults fall in the overweight or obese range by WHO standards.
What this means:A BMI of 26 classified as “overweight” places you below the US national median for adults. This is not an argument that BMI 26 is “fine,” it means the population comparison context matters. Being below the national average for BMI does not mean your weight presents no health risk. It means you’re comparing your number to the correct benchmark.
BMI for Children and Teenagers: Different Rules Apply
The WHO and CDC use a completely different system for children and teens aged 2–19: BMI-for-age percentiles. Adult thresholds (18.5, 25, 30) do not apply to children. Instead, BMI is plotted against growth charts based on age and sex, and health categories are assigned based on where a child falls in the population distribution:
| Percentile | Category |
|---|---|
| Below 5th percentile | Underweight |
| 5th to 84th percentile | Healthy weight |
| 85th to 94th percentile | Overweight |
| 95th percentile and above | Obesity |
Use the CDC’s separate BMI-for-age calculator for children and teens. The adult calculator on this page is validated for ages 20 and older. For children ages 2–19, adult BMI numbers are meaningless without the age and sex percentile context.
What to Do After Getting Your BMI: The Better Measurements
BMI is a starting point. These three additional measurements provide a more complete picture of metabolic health risk and require nothing more than a measuring tape:
1. Waist Circumference
Waist circumference measures visceral fat, the metabolically active fat stored around abdominal organs, which BMI cannot detect. US guidelines (NIH): - Men: increased risk above 94 cm (37 inches), high risk above 102 cm (40 inches) - Women: increased risk above 80 cm (31.5 inches), high risk above 88 cm (34.6 inches)
2. Waist-to-Height Ratio (WHtR)
A 2010 study of 11,000 subjects published in Obesity Reviews found waist-to-height ratio was a better predictor of heart attack, stroke, and death than BMI. The practical rule: your waist circumference should be less than half your height. WHtR = Waist circumference ÷ Height. Target: below 0.5 for most adults. Example: 5'8" (68in) with 34in waist = 0.50. Boundary. 36in waist = 0.53 elevated risk.
3. Body Fat Percentage
The gold-standard measurement of body composition. Healthy ranges per American Council on Exercise: - Men: essential 2-5%, athletes 6-13%, fitness 14-17%, acceptable 18-24%, obese 25%+ - Women: essential 10-13%, athletes 14-20%, fitness 21-24%, acceptable 25-31%, obese 32%+ DEXA scan (most accurate), hydrostatic weighing, or BIA devices provide body fat percentage.
BMI correlates with body fat at a population level, but cannot tell you your individual percentage. Two people with the same BMI can have wildly different body fat percentages depending on muscle mass, bone density, and fat distribution.
What BMI Cannot Tell You: The Honest Limitations
Muscle mass
A heavily muscled person, a competitive athlete, or a bodybuilder may have a BMI in the overweight or obese range despite having very low body fat. This is the most commonly cited BMI limitation. It applies to a small percentage of the general population but is a meaningful concern for active individuals.
Age-related changes
Older adults tend to lose muscle mass (sarcopenia) while maintaining or gaining fat mass. A person in their 70s can have a “healthy” BMI while carrying clinically significant excess body fat, particularly visceral fat. The waist circumference measurement is more predictive in this population.
Fat distribution
BMI doesn’t indicate where on your body fat is stored. Subcutaneous fat (under the skin) is metabolically relatively benign. Visceral fat (around organs) is metabolically active, inflammatory, and associated with insulin resistance, type 2 diabetes, and cardiovascular disease. Two people with the same BMI can have very different health profiles depending on fat distribution.
Bone density
People with higher bone mineral density may register as overweight by BMI without carrying excess fat. Conversely, people with osteoporosis may appear “normal” BMI while actually being metabolically under-lean.
Frequently Asked Questions
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