Our body fat calculator uses the U.S. Navy circumference method — one of the most accurate ways to estimate body fat without expensive equipment. Simply enter your height, waist, neck (and hip for women) measurements to get your body fat percentage, lean body mass, and fat mass. We also show body fat categories and healthy ranges for your age and gender.
Measure at belly button level, relaxed
Narrowest point below Adam's apple
Widest point of hips/buttocks
Navy Method
Uses U.S. Navy formula, accurate within 3-4% of DEXA scans. Measure in the morning for consistency.
Select gender and enter your age, weight, and height accurately.
Measure at navel level (not narrowest point). Stand relaxed, don't suck in stomach.
Measure at the narrowest point, just below your Adam's apple.
Measure at the widest point of your hips/buttocks for accurate results.
The Navy body fat formula uses circumference measurements to estimate body fat. For men, it uses waist and neck measurements. For women, it also includes hip measurement. This formula has been validated against hydrostatic weighing and is accurate to within 3-4%.
Body Fat % = 495 / (1.0324 - 0.19077×log10(waist-neck) + 0.15456×log10(height)) - 450
Measure in the morning before eating for most consistent results
Use a flexible tape measure and don't pull too tight
Measure waist at navel level (not at the narrowest point)
Measure neck at the narrowest point below the Adam's apple
For women, measure hips at the widest point
Body fat varies throughout the day — measure at the same time for tracking
The Navy method is accurate to within 3-4% of DEXA scans
Our free body fat calculator uses the accurate U.S. Navy method to estimate your body fat percentage from simple measurements. No expensive equipment needed — just measure your waist, neck (and hip for women) to get your body fat %, lean body mass, fat mass, and see how you compare to healthy ranges.
The most accurate home method is the Navy formula using circumference measurements.
For men, measure:
For women, also measure hip at widest point.
Our calculator applies the Navy formula to estimate body fat percentage accurate to within 3-4% of lab methods.
The Navy method using actual body measurements is more accurate than BMI-based estimates.
BMI can't distinguish muscle from fat — a muscular person and overweight person may have the same BMI but very different body fat.
Our calculator shows both methods for comparison.
Body fat categories differ by gender.
For men:
For women:
Our calculator shows your category.
Besides body fat percentage, we calculate your lean body mass (muscle, bones, organs) and fat mass.
Knowing these helps you track fitness progress — you want to lose fat while preserving or building lean mass.
Lean body mass also determines your calorie needs.
The Navy method estimates body fat from tape measurements — for men, from waist and neck circumference and height; for women it adds the hips.
Using measurements for an example man (waist 35.4 in, neck 15.75 in, height 70.87 in) the formula returns about 11.9% body fat.
It requires no special equipment and correlates reasonably with more expensive methods, which is why the U.S. Navy and this calculator use it, though it is an estimate, not a lab measurement.
Healthy body fat differs by sex because women carry more essential fat.
The American Council on Exercise lists general ranges:
Ranges shift slightly upward with age.
These are guidelines, not strict cutoffs — health depends on overall fitness, fat distribution, and metabolic markers like blood lipids, which you can check with our cholesterol calculator, not body fat percentage alone.
Body fat splits into essential fat — needed for hormones, organ protection, and (in women) reproductive function — and storage fat held in adipose tissue.
Dropping below essential levels (roughly 2-5% men, 10-13% women per ACE) is dangerous and unsustainable.
This is why 0% body fat is impossible and why extreme leanness harms health.
Healthy goals keep essential fat intact while managing excess storage fat.
BMI uses only height and weight and cannot distinguish muscle from fat, so a muscular athlete can register as 'overweight' while carrying low body fat.
Body fat percentage measures composition directly and is more informative for fitness.
The ACSM recommends using body composition alongside BMI rather than either alone.
For most people BMI is a quick screen; body fat percentage better reflects what training and diet are actually changing.
Methods vary in cost and accuracy.
The American Council on Exercise notes consistency matters most — track the same method over time rather than comparing across methods, since each has its own bias.
Reducing body fat requires a modest calorie deficit to lose fat, combined with resistance training and adequate protein to preserve (or build) muscle — since the percentage depends on both fat and lean mass.
Cardio adds to the deficit and improves fitness.
The ACE and ACSM emphasize a sustainable pace; rapid loss sacrifices muscle, which raises body fat percentage even as weight falls.
Patience and consistency beat crash approaches.
Frequent mistakes include:
Measure under consistent conditions, stick to one method for tracking trends, treat any single reading as an estimate with error, and target a healthy range rather than the lowest possible number.
Data sourced from trusted institutions
All formulas verified against official standards.