Get instant, accurate results using the clinically-validated US Navy method. Understand your health metrics with beautiful visual gauges and personalized insights.
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Visual breakdown of your health metrics
Calculate your BMI to see personalized health insights here.
Calculate your body fat to see personalized health insights here.
Medical Disclaimer: These results are for informational purposes only and are not a substitute for professional medical advice. Always consult a qualified healthcare provider before making health decisions.
Body Mass Index (BMI) is a numerical value derived from a person's height and weight. Developed by Belgian statistician Adolphe Quetelet in the 1830s, it provides a simple, quick screening tool to categorize individuals into weight status categories.
The formula is straightforward:
BMI is widely used by healthcare professionals as a first-pass screening tool because it requires no special equipment — just a scale and a measuring tape. However, it does not directly measure body fat and has known limitations, particularly for athletes and older adults.
Body fat percentage is the proportion of your total body weight that is made up of fat tissue. Unlike BMI, it directly distinguishes between fat mass and lean mass (muscle, bone, organs, and water).
Your body contains two types of fat:
Monitoring body fat percentage gives a far more nuanced picture of health than weight or BMI alone, especially for people who exercise regularly or have unusual body compositions.
Both metrics measure health risk related to body composition, but they approach it differently. Here's how they compare:
| Feature | BMI | Body Fat % |
|---|---|---|
| Measures fat directly | No | Yes |
| Accounts for muscle mass | No | Yes |
| Equipment needed | Scale + ruler | Tape measure |
| Accuracy | Moderate | Higher |
| Best for | Population screening | Individual assessment |
For most people, using both metrics together provides the most complete picture. A person can have a "normal" BMI but high body fat (called "skinny fat" or normal-weight obesity), or a high BMI but low body fat (common in athletes).
While BMI is a useful population-level tool, it has several well-documented limitations when applied to individuals:
Clinicians typically use BMI alongside other measurements such as waist circumference, blood markers, and body fat percentage for a comprehensive assessment.
Everything you need to know about BMI and body fat
For adults aged 18–65, a healthy BMI is between 18.5 and 24.9. Below 18.5 indicates underweight; 25–29.9 is overweight; 30 and above is considered obese. Note that these thresholds may differ for certain ethnic groups — for example, some health organizations recommend lower cut-offs for people of Asian descent.
The US Navy method has been validated against hydrostatic weighing (considered the gold standard) and DEXA scanning. Studies show accuracy within 3–4% for most adults. Accuracy is highest when measurements are taken carefully and consistently. It can be slightly less accurate for very lean or very obese individuals.
Healthy ranges vary by sex and age. General guidelines from the American Council on Exercise:
Essential fat (required for survival) is 2–5% for men and 10–13% for women.
Yes, it's possible. Athletes and highly muscular individuals often have a high BMI (overweight or obese category) despite having low body fat and excellent cardiovascular health. BMI does not distinguish between fat mass and muscle mass. This is why body fat percentage and other health markers (blood pressure, cholesterol, blood sugar) are important alongside BMI.
Take each measurement twice and average the results for accuracy.
BMI is used for children and teens (aged 2–19) but is interpreted differently. Instead of fixed cut-offs, pediatric BMI is compared to age- and sex-specific percentiles. A child in the 85th–95th percentile is considered overweight; above the 95th percentile is obese. The adult BMI calculator on this page is not suitable for children.
For most people, checking once a month is sufficient to track meaningful trends without getting caught up in daily fluctuations (which can be caused by hydration, meals, and clothing). If you're actively trying to lose fat or build muscle, measuring every 2–4 weeks alongside progress photos can be motivating and informative.
Subcutaneous fat is stored just beneath the skin — it's the fat you can pinch. While excess amounts are a concern, it's relatively less dangerous. Visceral fat is stored deep in the abdomen, surrounding organs like the liver and pancreas. It's metabolically active and strongly linked to insulin resistance, type 2 diabetes, heart disease, and inflammation. A large waist circumference is an indicator of excess visceral fat.
No. BMI and body fat calculators designed for general adults are not appropriate for pregnant women. Body weight and composition change dramatically during pregnancy for healthy reasons. Pregnant women should discuss weight management with their OB-GYN or midwife who can use pregnancy-specific growth charts and guidelines.