How accurate is the US Navy method?

Within ~3 to 4 percentage points of DEXA for most adults. Reliable enough to track changes over a 4-12 week phase, not precise enough for an absolute number you stake decisions on. The tape doesn't lie, but how you hold it does, so consistency matters more than the exact value.

Where exactly do I measure?

Neck just below the Adam's apple, head facing forward, tape level. Waist at the navel for men, at the narrowest point above the navel for women. Hip at the widest point (women only). Stand relaxed, no sucking in. Measure on bare skin in the morning before eating for the most consistent reading.

Why does the women's formula add hips?

Body fat tends to sit lower (hips, thighs) in women and higher (around the abdomen) in men. The original Navy researchers found that including hip circumference dramatically improved women's accuracy. The math reflects how fat distributes differently across sexes.

What's a better method than US Navy tape?

DEXA scans are the practical gold standard (1-3% error). BodPod is good (~2-3%). Skinfold calipers in trained hands are 2-5%. Bioelectrical-impedance scales are surprisingly noisy (5-7%) and very hydration-dependent. For most people, the Navy method beats a bathroom scale and costs nothing.

What about athlete-range numbers, are they safe long-term?

Athletic body-fat ranges (men 6-13%, women 14-20%) are achievable for many but expensive in time, food discipline, and life flexibility. Essential-fat levels (men <6%, women <14%) cost real things, hormones, recovery, mood. Most adults are better off in the fitness range and using the rest of their attention elsewhere.

I'm lifting and gaining weight, but body fat % isn't budging. What gives?

That's actually good. If body fat % is steady while weight climbs, lean mass is going up, that's the goal of a lean bulk. If body fat % is dropping while weight stays flat, that's recomp working. Look at the trend in the number over 4-6 weeks, not week to week.

All tools

Body fat calculator

A free tape-measure body fat estimate.

Q: I'm lifting and gaining weight, but body fat % isn't budging. What gives?

That's actually good. If body fat % is steady while weight climbs, lean mass is going up, that's the goal of a lean bulk. If body fat % is dropping while weight stays flat, that's recomp working. Look at the trend in the number over 4-6 weeks, not week to week.

The US Navy formula: three (or four) tape measurements and a result within ~3 to 4 points of DEXA. Useful for trends, not absolute precision. Bring a soft tape.

Your measurements

Sex

Measurement unit

Height

Neck

Measure just below the Adam’s apple, head facing forward, tape level.

Waist

Men: measure at the navel, relaxed, tape level.

Your body fat estimate

US Navy method

17.5%

Estimated body fat

Fitness· M

5%15%25%35%45%

Men's reference range · Fitness

14–17%

Fitness range, lean and athletic-looking, more sustainable than athlete range for most adults with full lives.

The US Navy method is a tape-measure estimate, expect ~3 to 4% error compared to DEXA. Use it for trends over weeks, not absolute precision. Same measurer, same conditions, same time of day matters more than the formula.

For real precision

When tape-measure isn’t enough.

If the absolute number matters (competition prep, clinical context, settling a bet with yourself), step up to a real body-composition measurement:

DEXA scan · 1–3% error
Practical gold standard. Bonus: regional fat distribution, lean mass, bone density.
BodPod (air displacement) · ~2–3% error
Good when available; less common than DEXA, less informative.
Hydrostatic weighing · ~2% error
The classic research standard. Hard to find outside a sports-science lab.
Skinfold calipers (3 or 7 site) · 2–5% error
Cheap, fast, very tester-dependent. A trained measurer is everything.

For most people, the Navy method above is good enough to track a 12-week phase. Spend the DEXA money on a coach instead.

The math

Why a tape can estimate body fat.

Where fat hides. Across large populations, fat sits in predictable places: around the midsection for men, around the hips and lower body for women. Neck circumference scales with frame size (a proxy for lean mass), waist scales with abdominal fat, and hip scales with lower-body fat. The ratio between those tells a story.

The Navy formula. Developed by researchers at the Naval Health Research Center in the 1980s, the formula is a regression fit against hydrostatic-weighing body fat from a Navy population. It turns out three (men) or four (women) measurements is enough to predict body fat within a few percentage points for most adults.

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.

How to take the measurements. Same time of day, same conditions, same tape, every time. Morning, before eating, on bare skin. Tape level (use a mirror), snug but not compressing. The number you’ll see week to week is more about consistency than precision, hold the tape the same way and the trend will be honest.

What this can’t do. The Navy method assumes a typical body shape. Very tall lifters with wide necks, petite women with narrow frames, and anyone with unusual fat distribution will get noisier numbers. If you need precision, DEXA is the practical gold standard.

Worked example

Male, 5′10″, neck 15, waist 34.

Height 70 in, neck 15 in, waist 34 in. Plug into the men’s formula:

BF% = 86.010 × log₁₀(34 − 15) − 70.041 × log₁₀(70) + 36.76

= 86.010 × 1.279 − 70.041 × 1.845 + 36.76 ≈ 109.99 − 129.21 + 36.76 ≈ 17.5%.

That lands in the fitness range for men (14–17% is the standard band, with 18–24% average). Reasonable starting point for a lean-bulk or a maintenance phase.

FAQ

Honest answers.

How accurate is the US Navy method?: Within ~3 to 4 percentage points of DEXA for most adults. Reliable enough to track changes over a 4-12 week phase, not precise enough for an absolute number you stake decisions on. The tape doesn't lie, but how you hold it does, so consistency matters more than the exact value.
Where exactly do I measure?: Neck just below the Adam's apple, head facing forward, tape level. Waist at the navel for men, at the narrowest point above the navel for women. Hip at the widest point (women only). Stand relaxed, no sucking in. Measure on bare skin in the morning before eating for the most consistent reading.
Why does the women's formula add hips?: Body fat tends to sit lower (hips, thighs) in women and higher (around the abdomen) in men. The original Navy researchers found that including hip circumference dramatically improved women's accuracy. The math reflects how fat distributes differently across sexes.
What's a better method than US Navy tape?: DEXA scans are the practical gold standard (1-3% error). BodPod is good (~2-3%). Skinfold calipers in trained hands are 2-5%. Bioelectrical-impedance scales are surprisingly noisy (5-7%) and very hydration-dependent. For most people, the Navy method beats a bathroom scale and costs nothing.
What about athlete-range numbers, are they safe long-term?: Athletic body-fat ranges (men 6-13%, women 14-20%) are achievable for many but expensive in time, food discipline, and life flexibility. Essential-fat levels (men <6%, women <14%) cost real things, hormones, recovery, mood. Most adults are better off in the fitness range and using the rest of their attention elsewhere.
I'm lifting and gaining weight, but body fat % isn't budging. What gives?: That's actually good. If body fat % is steady while weight climbs, lean mass is going up, that's the goal of a lean bulk. If body fat % is dropping while weight stays flat, that's recomp working. Look at the trend in the number over 4-6 weeks, not week to week.

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A single number is a snapshot. A coach watches the trend, adjusts the plan, and keeps you honest about what to chase and what to leave alone. Let’s talk.

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A note on the numbers. These tools use established formulas (Mifflin-St Jeor, AMDR macros, healthy-range references) and population averages. Treat results as a starting point, not personalized medical advice. Your individual needs may differ based on body composition, training history, and medical context. Consult a qualified healthcare professional before making significant changes to your nutrition or training, especially if you have a pre-existing condition. See our full fitness and medical disclaimer.