Body Fat Percentage Calculator
Estimate body fat using the US Navy circumference method or the 3/7-site Jackson-Pollock caliper formula. Get fat mass, lean mass, and your fitness category.
Your Measurements
Your Results
Body Fat Categories
This calculator provides estimates, not clinical measurements. Consult a healthcare professional for medical decisions.
How it works
US Navy Method
Uses waist, neck, and hip (women) circumferences. No equipment needed, highly accessible.
Caliper Methods
3-site and 7-site Jackson-Pollock skinfold formulas. More accurate with a trained measurer.
What you get
Body fat %, fat mass, lean mass, BMI, your fitness category, and a full reference chart.
Not medical advice. This calculator gives a general estimate based on the values you enter. It cannot account for your medical history, medication or body composition. Talk to a doctor or a registered dietitian before acting on any result.
How this body fat calculator estimates composition without a scan
Body fat percentage tells you something BMI never can, how much of your weight is fat versus everything else, muscle, bone, organs, water. Getting that number precisely requires a DEXA scan or hydrostatic weighing, equipment nobody keeps at home. This tool instead uses two field methods that have been validated against those lab standards closely enough to be genuinely useful: the US Navy circumference method and the Jackson-Pollock skinfold caliper method, in both 3-site and 7-site versions.
Every measurement you type stays in your browser. The formulas run as plain JavaScript on your device, there’s no upload and nothing is logged once you navigate away.
The Navy method: circumferences and a logarithm
This is the default method because it needs no special equipment, just a tape measure. It comes from a 1984 technical report by Hodgdon and Beckett at the Naval Health Research Center, developed to give the US Navy a fast, equipment free way to estimate body fat for fitness standards. The formula uses circumference measurements plugged into a regression equation built on log base 10.
That 495-over-something-minus-450 shape isn’t arbitrary, it comes from the Siri equation, which converts an estimated body density into a fat percentage. The log10 terms inside the Navy formula are actually estimating density from circumferences first, then Siri’s conversion turns density into the fat percentage you see. Two published formulas stacked into one line of code.
The caliper methods: Jackson-Pollock
Switch tabs and you get skinfold caliper measurements instead of tape measure circumferences. Jackson and Pollock published their generalized equations in 1978, based on pinching a fold of skin and subcutaneous fat at standardized sites and measuring its thickness in millimetres with a caliper.
| Method | Sites (Male) | Sites (Female) |
|---|---|---|
| 3-site | Chest, abdomen, thigh | Tricep, suprailiac, thigh |
| 7-site | Chest, midaxillary, tricep, subscapular, abdomen, suprailiac, thigh (both sexes) | |
Same Siri conversion at the end, 495 over density minus 450. The difference between methods is entirely in how density gets estimated in the first place, circumferences for Navy, skinfold thickness plus age for Jackson-Pollock. The 7-site version generally tracks closer to lab measured density than the 3-site shortcut, since more sampling points average out measurement noise and individual fat distribution quirks.
Category bands and what they output
Male categories
Essential fat 2 to 5 percent, athletic 6 to 13, fitness 14 to 17, average 18 to 24, obese 25 and above. Essential fat is the minimum needed for basic physiological function, going below it for extended periods carries real health risk.
Female categories
Essential fat 10 to 13 percent, athletic 14 to 20, fitness 21 to 24, average 25 to 31, obese 32 and above. Women carry a higher essential fat floor than men, tied to reproductive and hormonal function.
The tool also reports fat mass and lean mass in kilograms or pounds, computed by multiplying your body weight by the fat percentage and subtracting the rest, plus your BMI for cross reference against the more familiar height and weight ratio.
- Hodgdon & Beckett, Naval Health Research Center Technical Report, 1984, origin of the Navy circumference method.
- Jackson & Pollock, British Journal of Nutrition, 1978, the generalized skinfold equations.
- Siri, 1961, the density-to-fat-percentage conversion used by both methods here.
- American Council on Exercise, Body Fat Categorization for a second reference on the category bands.
This calculator is an educational estimate, not a clinical body composition analysis. Field methods like these carry a margin of error of roughly 3 to 4 percentage points against DEXA scan results, even when done carefully. Consult a healthcare provider or exercise physiologist for a formal assessment if body composition is relevant to a medical decision.
Measurement contexts
Tracking body recomposition progress alongside the scale during a training block, setting a baseline before a cut or bulk, military and law enforcement fitness standard estimation using the same Navy method these agencies actually use, and giving a coach a quick composition number between formal testing sessions.
Questions About the Body Fat Percentage Calculator
For men, 14-24% is considered average and 6-17% is athletic or fitness level. For women, 21-31% is average and 14-24% is athletic or fitness. Essential fat (the minimum for organ function) is 2-5% for men and 10-13% for women.
The US Navy method has a margin of error of roughly 3-4% compared to DEXA scans. It works best for people with typical body proportions. Measurement accuracy is critical — small errors in circumference lead to meaningful differences in the result.
Waist: measure horizontally at the navel. Neck: measure just below the larynx (Adam’s apple), sloping slightly downward at the front. Hip (women only): measure at the widest point. Use a flexible tape measure and keep it level. Do not suck in or flex.
Lean body mass is your total weight minus your fat mass. It includes muscle, bone, organs, and water. Tracking lean mass alongside body fat gives a more complete picture of body composition than weight alone — you can lose fat while maintaining or gaining lean mass.
With proper technique, the 7-site Jackson-Pollock caliper formula is generally more accurate than the Navy method for most populations. The 3-site caliper is a good middle ground. All three methods are less precise than DEXA or hydrostatic weighing. Consistency matters most when tracking progress over time.
The Jackson-Pollock caliper formulas include age as a variable because body density changes with age even at similar skinfold thicknesses. Older individuals tend to have more internal fat relative to subcutaneous fat, so age adjusts the density-to-fat-percentage conversion.
Essential fat is the minimum amount of fat required for normal physiological function, including hormone production, organ protection, and nerve insulation. For men this is approximately 2-5%, for women 10-13%. Going below these levels is dangerous and associated with serious health complications.
From the blog
The research behind the numbers
Where these formulas came from and what the studies actually showed.
