A scale tells you weight. Body fat percentage tells you what kind of weight. This calculator uses the U.S. Navy Method, three simple measurements with a soft tape, to estimate body fat % within 3% of a DEXA scan, free, with no calipers required.
The U.S. Navy Method estimates body fat using waist, neck, and height (plus hip for women), typically within ±3% of DEXA. Healthy lean ranges: men 10-17%, women 18-25%. Athletic men sit 6-13%; athletic women 14-20%. Body fat below 5% (men) or 12% (women) is competition territory and not sustainable. Pairs with BMI and ideal body weight to give a complete picture.
Source: Hodgdon JA, Beckett MB. Naval Health Research Center 1984↑ These are example numbers. Calculate above to replace them with yours.
A 22-year-old at 12% BF and a 55-year-old at 12% BF are not the same picture. Body fat naturally rises with age, and what's "optimal" shifts with it. Below are the standardized ranges from ACE and ACSM.
| Age | Athletic | Fitness | Average | Above average |
|---|---|---|---|---|
| 20-29 | 6-13% | 14-17% | 18-24% | 25%+ |
| 30-39 | 7-14% | 15-18% | 19-24% | 25%+ |
| 40-49 | 8-15% | 16-20% | 21-25% | 26%+ |
| 50-59 | 9-17% | 18-21% | 22-26% | 27%+ |
| 60+ | 10-18% | 19-22% | 23-27% | 28%+ |
Essential fat (men): 2-5% • Essential fat (women): 10-13%. Below essential = clinically dangerous.
Diet and training matter. But for many men over 30, the bigger lever is hormones and metabolic health. Here's the playbook our physicians prescribe, ranked by impact.
Average ~15% body weight reduction in 68 weeks (STEP-1 trial), with disproportionate visceral fat loss. The single most effective pharmacological tool for bringing body fat down, especially when willpower alone has stalled.
Learn about Semaglutide Best-in-classDual GIP/GLP-1 agonist. SURMOUNT-1 trial: ~20.9% mean body weight reduction at 72 weeks, the largest pharmacological weight-loss result ever published. If you want maximum fat loss, this is the lever.
Learn about Tirzepatide If your testosterone is lowLow testosterone causes visceral fat gain and lean-mass loss in men. Restoring T (when clinically deficient) shifts body composition independently of calories, typically 4-7% reduction in fat mass with simultaneous lean gain.
Learn about TRT Preserve fertilityFor men with low T who want fat loss benefits without shutting down their own production. Raises endogenous testosterone, improves body composition, preserves fertility, useful for younger men or those planning families.
Learn about Enclomiphene Cellular metabolismNAD+ is the master coenzyme that powers mitochondrial energy production and fat oxidation. Restoring NAD+ supports the cellular machinery your body uses to actually burn fat, especially relevant after age 35 when NAD+ levels decline sharply.
Learn about NAD+ Test then treatBefore guessing, measure. Our optimization panel includes testosterone, free T, SHBG, fasting glucose, HbA1c, lipids, thyroid, cortisol, and inflammatory markers. Get the bottleneck identified, then build the protocol.
See lab panelsBody fat % is one number. These four tools fill in the rest of the system, calories, protein, hormones, and aging.
Hand-picked guides from our physician-edited library covering the science of fat loss, body composition, and hormonal levers.
Garbage in, garbage out. Use a soft, flexible tape (a cloth or fiberglass tape works, not metal). Measure on bare skin, first thing in the morning if possible, and pull the tape snug but not compressed against the skin.
The U.S. Navy method (Hodgdon & Beckett, 1984) uses log-transformed circumference ratios:
Men: BF% = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Women: BF% = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
All measurements in inches. Validation studies against hydrostatic weighing show ~3-4% mean error, comparable to skinfold calipers in untrained hands and only slightly worse than DEXA in non-extreme physiques.
It depends on what you're optimizing for:
Body fat % is dramatically more useful than BMI for individuals. BMI cannot distinguish a 200-lb lifter at 12% BF (athletic) from a 200-lb sedentary man at 32% BF (obese), the BMI is identical. Body fat %, by contrast, captures the actual signal: how much of your weight is fat vs. lean mass.
The exception: BMI is fine for population-level epidemiology and rough screening. For your personal target, body fat % beats it. Use our BMI calculator for the quick screen and this tool for the real target.
For non-extreme physiques (BMI 18-35), the Navy method tracks within ~3% of DEXA scans on average. It loses accuracy in two cases: very lean physiques (skews high) and very obese physiques (skews low). For everyone in between, it's the most accurate at-home method without specialized equipment.
Every 2-4 weeks if actively cutting or bulking. Body fat doesn't change in days, give it time. More frequent measurement causes you to chase noise. Same conditions every time: morning, fasted, after the bathroom, before training.
It usually doesn't actually, but circumferences can shift in confusing ways early in lifting. Your waist may temporarily increase from spinal-erector and oblique growth. Your neck may grow from traps and SCM. Trust trends over 8+ weeks, not week-to-week noise.
If you're a man over 30 and 5+ points above the optimal range, the order of operations is usually: (1) get a comprehensive lab panel including testosterone, SHBG, glucose, HbA1c, and lipids, (2) calculate maintenance calories with our TDEE calculator and protein target with our protein calculator, (3) review whether GLP-1 therapy or TRT is appropriate based on your labs, (4) start a structured lifting program 3-4 days per week. The single biggest mistake is trying willpower alone when the underlying physiology is broken.
Below 5% (men) or 14% (women) chronically is dangerous, it disrupts testosterone, immune function, sleep, and bone density. If you're a competitive athlete it may be temporarily appropriate; for everyone else, it's a sign to eat more and train smarter, not less.
In SURMOUNT-1, FDA-approved branded tirzepatide produced an avg 20.9% body-weight reduction at 72 weeks. Compounded preparations are not FDA-approved. Pair GLP-1 therapy with adequate protein (0.7-1.0g per lb of goal weight) and resistance training to support lean-mass preservation during weight loss.
How this tool calculates
Body fat percentage is estimated using the Hodgdon-Beckett U.S. Navy circumference method, which uses waist, neck, and height (plus hip for women). Validation studies show accuracy within approximately ±3% body fat compared to DEXA in non-extreme physiques. Less accurate for elite athletes or BMI >40.
Peer-reviewed sources
Important. This tool is provided for educational purposes only and does not constitute medical advice, diagnosis, or treatment. The tool does not prescribe medication, recommend specific dosing, or substitute for clinical evaluation. Compounded medications referenced anywhere on this site are not FDA-approved; the FDA does not verify the safety, effectiveness, or quality of compounded drugs. Treatment decisions are made only by a licensed U.S. physician after individual patient evaluation.