Estimate your body fat percentage using the trusted US Navy circumference method. Get fat mass, lean body mass, and where you stand against healthy ranges — all instantly.
Tap a unit, fill in your details — body fat updates live.
Estimated Body Fat
Body Fat %
18.5%
Fat Mass
32.4 lbs
Lean Mass
142.6 lbs
Category
Average
| Category | Men | Women | Your Status |
|---|
Healthy Ranges
Body fat percentage varies by sex. Below the essential level is dangerous; above the obese threshold raises health risk.
Measurement Tips
The Formula
The US Navy method estimates body fat from circumference measurements and height using logarithmic regression equations. It was developed in 1984 from data on 600+ Navy personnel and remains one of the most accessible field methods today.
From the resulting body fat percentage, we derive fat mass (weight × body fat) and lean body mass (the rest — muscle, bone, organs, water).
US Navy Equation
About This Tool
A body fat calculator estimates the percentage of your total weight that is fat — a far more useful number than weight or BMI alone. Two people at the same weight and height can have wildly different body compositions; one might be athletic and lean, the other carrying excess fat.
This tool uses the US Navy circumference method, developed by the Naval Health Research Center. It requires only a tape measure, takes seconds to apply, and is accurate to within ±3–4% of a DEXA scan for most people. It outperforms BMI for athletes and people with above-average muscle mass.
Once you have your body fat percentage, you can derive fat mass and lean body mass — the two numbers that actually move when you're cutting fat or building muscle. Tracking these over weeks is far more informative than chasing scale weight.
Navy-Grade Accuracy
±3–4% vs. DEXA — better than BMI for athletes.
Imperial & Metric
Switch between inches/lbs and cm/kg instantly.
Healthy Range Check
Instantly see where you fall — Essential to Obese.
Live Composition Chart
Visual breakdown of fat mass vs. lean body mass.
Sex-Specific Formula
Different equations for men and women — more accurate for both.
Tape-Measure Only
No calipers, no scales beyond your bathroom one — done in 60 seconds.
An accurate body fat estimate in under a minute.
Choose Imperial (inches, lbs) or Metric (cm, kg). Inputs convert automatically.
Sex changes the formula. Age and height anchor the calculation and the range comparison.
Neck below the larynx, waist at the navel (men) or narrowest point (women). Women: add hip at the widest.
Used only to convert body fat % into fat mass and lean body mass — the more useful tracking numbers.
Your body fat %, category pill (Essential → Obese), fat mass and lean mass — all update as you type.
The Reference tab shows category cut-offs for men and women side-by-side with your current status.
Everything you need to know about measuring body fat.
The US Navy circumference method has an accuracy of about ±3–4% compared to DEXA scans. It's reliable and equipment-free, though it slightly under-predicts for very lean people and over-predicts for very heavy individuals. Hydrostatic weighing and DEXA are more accurate but require specialized equipment.
Measure at the navel for men and the narrowest natural indent for women. Keep the tape level — not slanting — snug against the skin but not compressing it. Breathe normally and don't suck in. Take the measurement at the end of a normal exhale.
Female body fat distribution differs from men's — women carry more fat around the hips and thighs. The US Navy formula for women incorporates hip circumference to account for this, substantially improving accuracy compared to using only waist and neck.
For men: Essential 2–5%, Athletic 6–13%, Fit 14–17%, Average 18–24%, Obese 25%+. For women: Essential 10–13%, Athletic 14–20%, Fit 21–24%, Average 25–31%, Obese 32%+. The "Fit" range is a healthy long-term target for most people.
BMI uses only weight and height, so it labels muscular athletes as "overweight" and skinny-fat people as "normal". Body fat percentage measures what actually matters: how much of your weight is fat versus muscle, bone, and organs. It's especially better for athletes, older adults, and anyone strength-training.
Fat mass = weight × body fat %. Lean body mass = everything else (muscle, bone, organs, water). Tracking both over time is more useful than scale weight. If you're cutting fat the right way, fat mass drops and lean mass stays put; if you're losing muscle, lean mass drops too — a warning sign to eat more protein and lift weights.
Every 2–4 weeks is plenty. Body fat changes slowly — daily measurements only pick up water-weight fluctuations and add anxiety. Measure first thing in the morning, on an empty stomach, before working out, under the same conditions each time.