Navy Body Fat Calculator
Estimate body fat percentage and lean body mass from neck, waist, and hip measurements. The tape method used by the U.S. Navy since 1984 — free, fast, and surprisingly close to gold-standard methods when measured carefully.
Your Measurements
Your Results
- Estimated Body Fat
- —%
- Navy method (tape measurement)
- ACSM Band
- Lean Body Mass
Enter weight (optional) to see lean body mass and fat mass.
Enter height, neck, and waist to see an estimate.
How the Navy Body Fat Method Works
The U.S. Navy adopted the circumference-based body fat estimatein 1984 (Hodgdon & Beckett) as a low-cost alternative to skinfold callipers and hydrostatic weighing. The equations were developed against hydrostatic-weighing references using regression on neck, waist, hip, and height measurements.
For men, the formula is:
BF% = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
For women, the formula adds hip circumference:
BF% = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
All measurements are in inches. The calculator accepts metric input and converts internally.
How accurate is it?
Across published validation studies the Navy method typically lands within ±3–4% body fat of DEXA for most adults — roughly the same accuracy band as a well-trained skinfold technician and noticeably better than consumer BIA scales. It tends to overestimate BF% in very lean, muscular bodies (large necks pull the inputs in the wrong direction) and underestimate in bodies that carry weight outside the waist. For most desk-job-to-recreational-athlete bodies it is the best free method available.
How to take the measurements
- Neck:just below the larynx, tape angled slightly downward toward the front. Don’t pull the tape tight.
- Waist (men):horizontal, at the navel, after a normal exhale. Don’t suck in.
- Waist (women): at the narrowest part of the torso — usually 1–2 inches above the navel.
- Hip (women): the widest point of the buttocks, feet together, weight evenly distributed.
- Use the same tape, same time of day, same hydration state when re-measuring. Day-to-day swings of ±1% are normal.
ACSM Body-Fat Bands
The category labels come from the American College of Sports Medicine body-fat classifications for adults:
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Women’s “essential” band sits roughly 10 percentage points higher than men’s because of reproductive and hormonal tissue requirements. Sustained body fat below the essential band is associated with hormonal disruption and bone- density loss — it is not a target for the general population.
What to do with the number
- Track the trend, not any single reading. A 7-measurement rolling average over two weeks is more useful than today’s snapshot.
- Pair body-fat % with weight on the scale — together they tell you whether you’re losing fat, muscle, or both.
- Feed the result into the TDEE Calculator With Body Fat, TDEE Calculator, or Macro Calculator to size your protein floor against lean body mass.
Body-Fat Measurement Reading
How to Measure Body Fat at Home
Navy tape vs. callipers vs. smart scales vs. visual estimation — accuracy, cost, and ease, with a pick for each kind of user.
DEXA vs. InBody vs. Callipers
The honest accuracy ranges for each method and which one to track over time.
What 15% Body Fat Looks Like (Men)
Visual descriptions across the men’s body-fat band, and how visual estimates compare to measured numbers.
What 25% Body Fat Looks Like (Women)
Women-specific banding, visual descriptors, and the case against chasing sub-15% as a non-athlete.
Body Fat % vs. BMI — Which Matters?
Why BMI breaks for muscular and ‘skinny fat’ bodies, and when it’s still useful as a sanity check.
TDEE Calculator
Now that you have a body-fat estimate, dial in maintenance calories and a deficit.