Calculate your body fat percentage using the U.S. Navy method
Uses simple body measurements for an accurate estimation
Measure just below the Adam's apple
Measure at belly button level
Body fat percentage is the proportion of your body weight that is composed of fat. Unlike BMI (Body Mass Index), body fat percentage distinguishes between fat mass and lean mass (muscles, bones, organs).
This calculator uses the U.S. Navy method, which is one of the most accurate formulas based on body measurements. This method has been scientifically validated and is widely used in fitness and health programs.
For decades, Body Mass Index (BMI) has been the standard measure to assess whether a person has a healthy weight. However, recent scientific studies in 2025 have shown that BMI has significant limitations as a health predictor, and that body fat percentage and muscle mass quantity are much more accurate indicators of physical wellbeing, disease risk, and longevity.
A University of Florida study published in June 2025 revealed that BMI fails as a predictor of future mortality risk, suggesting the calculation is deeply flawed. In contrast, body fat percentage measured directly through bioelectrical impedance proved to be a significantly stronger predictor of 15-year mortality in adults aged 20 to 49.
The main limitation of BMI is that it's based on the assumption that all weight exceeding determined values corresponds to fat mass. However, this assumption is fundamentally incorrect, as excess weight can correspond to increased muscle mass and/or bone mass.
Muscle and bone weigh more than fat, so BMI measurements can overestimate danger for people with muscular build or larger bone structure. Two people can have exactly the same BMI but very different body fat percentages, meaning their actual health risk is completely different.
A study revealed that approximately 72% of athletes were misclassified by their BMI, as their body fat percentage was in the normal range despite BMI classifying them as overweight or obese. The amount of muscle mass an athlete can develop causes that extra weight to be confused with excess fat when it's actually healthy muscle.
The current scientific consensus is clear: body mass index is a poor indicator in 1 out of every 4 individuals and should not be used in athletes as they carry greater muscle mass than the general population. BMI generally overestimates adipose tissue in those with greater body mass (like athletes) and underestimates excess fat in those with lower body mass.
Nearly 25% of people with normal weight according to BMI show abnormal metabolic profiles associated with obesity. This phenomenon is known as “Metabolically Obese Normal Weight” (MONW). These individuals have a normal BMI but high body fat content, and show higher prevalence of cardiometabolic dysregulation, metabolic syndrome, and cardiovascular disease risk factors.
Conversely, there are people with elevated BMI who are metabolically healthy due to their high muscle mass and low body fat. This demonstrates that BMI does not capture true body composition nor actual metabolic risk.
The most recent studies are conclusive: people with high body fat percentage measured directly have a 78% higher chance of dying from any cause than those with healthy body fat levels during 15 years of follow-up. Additionally, they have approximately 3.5 times higher likelihood of dying from heart disease.
Research indicates that body fat percentage is likely a better predictor than BMI for cardiovascular disease risk. Body fat percentage (BF%) directly correlates with risk factors for cardiovascular diseases and metabolic syndrome in both men and women.
Body fat percentage, especially abdominal fat, has a direct positive correlation with insulin resistance development, which is the precursor to prediabetes and type 2 diabetes. Studies show that among obese people, those who were insulin-sensitive had significantly lower total body fat and trunk fat values compared to insulin-resistant individuals.
In a 5.5-year follow-up, 37 of 76 insulin-resistant obese individuals developed prediabetes or type 2 diabetes, compared to 30 of 96 insulin-sensitive obese individuals. Obesity directly contributes to the development of cardiovascular risk factors, including dyslipidemia, type 2 diabetes, hypertension, and sleep disorders.
A healthy body fat percentage for men ranges between 8% and 19%, while women have a healthy range of 21% to 33%. Any values above these ranges indicate increased risks of problems with cardiovascular diseases, metabolic syndrome, insulin resistance, and premature mortality.
A revolutionary finding from recent research is that muscle mass relative to body height has independent predictive capacity for all-cause mortality in older adults. In a large nationally representative study of over 3,600 older Americans, those with greater muscle mass had better survival probabilities during 10 to 16 years of follow-up.
Most notably, this inverse relationship between muscle mass and mortality was not explained by traditional cardiovascular risk factors (dyslipidemia, hypertension, and inflammation) nor by glucose dysregulation (prediabetes, diabetes, insulin resistance). This suggests that relative muscle mass is an independent prognostic marker for survival in older adults.
Sarcopenia is the progressive loss of muscle mass and strength associated with aging. This condition affects 13% of people at age 65, 24% at age 70, and up to 50% in those over 80. It's estimated that sarcopenia affects 10%-16% of elderly people worldwide.
The consequences of sarcopenia are devastating: loss of strength and muscle mass is directly associated with increased mortality risk. Muscle mass loss is a significant predictor of all-cause mortality across different populations with different health states.
A study that followed over 3,000 older adults for several years found that those with sarcopenia had a 2-3 times higher risk of dying during the study period compared to those without sarcopenia. Additionally, the presence of sarcopenia was associated with a 3 to 4-fold increase in disability risk, regardless of age, sex, obesity, race, socioeconomic status, and comorbidity.
Sarcopenia has been linked to a wide range of serious health problems:
At any BMI level ≥22, people with low muscle mass had higher body fat percentage, higher diabetes probability, and higher adjusted mortality than other participants. This demonstrates that it's not just total weight that matters, but the specific composition of that weight.
In addition to muscle mass, muscle strength is a critical health indicator. A meta-analysis of 53,476 older adults found that the all-cause mortality risk comparing the weakest to strongest quintile of grip strength was 1.67. Grip strength was inversely associated with all-cause mortality, cardiovascular mortality, non-cardiovascular mortality, myocardial infarction, and stroke.
In very elderly populations (nonagenarians and centenarians), low muscle mass was associated with increased death risk (hazard ratio 1.54) in women in a Chinese cohort study.
Research clearly shows that the group with high muscle mass and low fat mass had lower risk of cardiovascular disease and total mortality, with adjusted risk ratios of 0.32 and 0.38 for cardiovascular disease and total mortality, respectively. This represents a risk reduction of approximately 68% for cardiovascular disease and 62% for total mortality.
In contrast, BMI alone cannot identify these crucial differences in body composition. Two people with the same BMI can have completely different risk profiles depending on their muscle versus fat composition.
To properly measure body composition, there are several more accurate methods than BMI:
Based on current scientific evidence, the most effective strategies to optimize body composition include:
Weight training or resistance training is essential for building and maintaining muscle mass. Recommended:
Dietary protein is crucial for muscle protein synthesis:
To reduce body fat without compromising muscle mass:
Adequate rest is fundamental for optimal body composition:
One of the most powerful concepts in modern fitness is body recomposition: the process of gaining muscle mass while losing body fat. In this scenario, the weight on the scale may remain the same or even increase slightly, but body composition improves dramatically.
For example: A person weighing 70 kg with 25% body fat (17.5 kg fat, 52.5 kg lean mass) could, after 6 months of proper training and nutrition, weigh 71 kg but with 18% body fat (12.8 kg fat, 58.2 kg lean mass). BMI would show a slight increase, but metabolic health would have improved significantly: 4.7 kg less fat and 5.7 kg more muscle.
To truly assess your health and fitness progress, you need to track:
Instead of setting a goal like “lose 10 kg”, composition-based goals are more meaningful and healthier:
The scientific evidence is conclusive: BMI is an obsolete and imprecise tool for assessing individual health. While it may have utility in large-scale population studies, it consistently fails at the individual level by not distinguishing between muscle mass and fat mass.
Body fat percentage and muscle mass quantity are significantly superior predictors of:
People with high muscle mass and low body fat have up to 68% lower risk of cardiovascular disease and 62% lower total mortality, regardless of what their BMI says. Conversely, people with “normal” BMI but high body fat percentage face significantly elevated health risks that BMI does not detect.
Sarcopenia and muscle mass loss represent serious health threats, especially in older adults, with 2-3 times higher mortality risks and 3-4 times higher disability risks. Maintaining and building muscle mass throughout life is not just a matter of aesthetics, but a fundamental strategy for longevity and quality of life.
Your goal should not be to reach an arbitrary number on the scale or a specific BMI. Instead, focus on optimizing your body composition: reducing body fat to healthy ranges while building and maintaining lean muscle mass. This is the true key to metabolic health, longevity, and physical wellbeing.
Use this calculator regularly to track your body fat percentage and lean muscle mass.
The numbers that really matter are not your weight or BMI, but the composition of that weight: how much is functional muscle that makes you stronger and healthier, and how much is fat that can increase your health risks. Measure, track, and optimize your body composition for a longer and healthier life.