Body Composition Calculators
Your body weight does not show how much of you is fat and how much is lean mass. These body composition calculators estimate your body fat percentage, body roundness, fat-free mass index (FFMI), metabolic age, and body type, and show how close you are to your natural muscular potential. Use them to track progress over time and set realistic goals for fat loss, muscle gain, or body recomposition. Every calculator is free, needs no signup, and runs in your browser. Results are educational estimates, not a diagnosis.
Pro Physique Calculator
Use our free pro physique calculator to measure symmetry, proportions, and muscle potential. Get your physique score out of 100 now.
FFMI Calculator
Calculate your Fat-Free Mass Index (FFMI) with this free FFMI calculator. Raw and normalized scores, muscularity tiers, and lean mass analysis.
Metabolic Age Calculator (BMR)
Use our free metabolic age calculator to discover your true body age and compare it to your real age with personalized improvement tips.
Body Fat Percentage Calculator
Use our body fat percentage calculator to measure Navy Method, get your category, lean mass, and fat mass instantly.
Maximum Muscular Potential Calculator
Free Maximum Muscular Potential Calculator. Estimate your natural lean mass ceiling using Casey Butt, Berkhan & FFMI formulas. Genetic muscle limit revealed.
Body Type Calculator
Use this free body type calculator to find your somatotype, ectomorph, mesomorph, or endomorph, from simple frame measurements, with personalized training and nutrition guidance.
Body Roundness Index Calculator (BRI)
Use this Body Roundness Index calculator with waist and height. Free BRI score, risk meter, and visceral fat insights.
Which calculator should I use?
Pick the one that matches your question:
- You want to know how much of your weight is fat. Use the Body Fat Percentage Calculator. You need a tape measure.
- You want to know how your waist and height compare. Use the BRI Calculator.
- You want to compare your muscle with your height. Use the FFMI Calculator. It needs your body fat percentage, so run the body fat calculator first.
- You want to know how far you can build muscle naturally. Use the Maximum Muscular Potential Calculator.
- You want to compare your metabolism with your age. Use the Metabolic Age Calculator.
- You want to understand your frame and build. Use the Body Type Calculator.
- You are working on proportions and symmetry. Use the Pro Physique Calculator.
How these calculators work
Body fat percentage is the share of your body weight that is fat. The U.S. Navy method estimates it from tape measurements and your height, and it gives your fat mass and lean mass too. FFMI divides your fat-free mass by your height squared, and a normalized version adjusts for height. BRI uses your waist and height to describe body shape.
BMI cannot tell fat from muscle, which is why body composition tools add useful detail. They are still estimates. A tape-measure result can differ from a DEXA scan by several percentage points, so measure the same way each time and watch the trend, not a single number.
Frequently Asked Questions
How accurate are body fat calculators?
They give a reasonable estimate, but they are not as precise as a DEXA scan. Results depend on how carefully you measure. Take your measurements at the same time of day, in the same spot, and compare results over weeks, not days.
What is the difference between BMI and body composition?
BMI compares your weight with your height and cannot tell fat from muscle. Body composition splits your weight into fat mass and fat-free mass, so a muscular person and a person with more body fat at the same weight look different.
What is a good FFMI?
It depends on your sex and height. In a 1995 study of athletes, those who did not use steroids rarely had a normalized FFMI above about 25. Treat that as a rough guide, not a hard limit, since individual results vary.
Is BRI better than BMI?
BRI uses your waist and height, so it reflects body shape, and some research suggests it may track body fat and visceral fat better than BMI. Other measures, such as waist-to-height ratio, have more research behind them, so use BRI as one measure, not the only one.
How often should I measure my body composition?
Most people measure every two to four weeks. Body composition changes slowly, and day-to-day readings swing with water and measuring errors, so a longer gap shows the real trend.
Sources
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center. 1984.
- Kouri EM, et al. Fat-free mass index in users and nonusers of anabolic-androgenic steroids. Clinical Journal of Sport Medicine. 1995;5(4):223-228.
- Thomas DM, et al. Relationships between body roundness with body fat and visceral adipose tissue emerging from a new geometrical model. Obesity. 2013;21(11):2264-2271.
- Carter JEL, Heath BH. Somatotyping: Development and Applications. Cambridge University Press; 1990.
Medical disclaimer
These calculators provide educational estimates and are not medical advice or a diagnosis. Talk to a doctor or registered dietitian if you have a medical condition, are pregnant, are under 18, or have a history of disordered eating. If tracking numbers affects how you feel about your body, take a break or talk to a healthcare professional.
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