How to Calculate Body Fat with the US Navy Body Fat Formula

The US Navy body fat formula is one of the most widely used methods for estimating body fat percentage, and for good reason: it requires nothing more than a flexible tape measure and your height. No calipers, no specialized equipment, no partner, no training.

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Developed by the US Department of Defense for military fitness assessments, the formula uses circumference measurements to estimate body fat. Males measure their neck and waist. Females measure their neck, waist, and hip. These measurements, combined with height, are plugged into a logarithmic equation that produces a body fat percentage estimate.

The method is less precise than caliper-based formulas or lab methods like DEXA, but its accessibility makes it the most practical starting point for anyone who wants to begin tracking body composition today with zero investment in equipment.

For a broader look at all body fat measurement methods, including caliper and lab-based options, see our complete guide to measuring body fat.

What You Need

Item	Notes
Flexible tape measure	Cloth or fiberglass. Not metal. Not elastic (it stretches over time).
Your height	In inches for the standard formula.
A calculator	The formula uses log10 (common logarithm). Any scientific calculator or smartphone calculator in scientific mode will work.

Measurement Locations for Males

Males need two circumference measurements: neck and waist.

Site	Location	Tips
Neck	Circumference just below the larynx (Adam's apple)	Tape level, not angled. Do not flare the tape at the front of the neck.
Waist	Circumference at the narrowest point of the torso, typically midway between the lowest rib and the top of the hip bone	Do not suck in your stomach. Stand relaxed, measure at the end of a normal exhale. The tape should be level all the way around.

Measurement Locations for Females

Females need three circumference measurements: neck, waist, and hip.

Site	Location	Tips
Neck	Circumference just below the larynx (Adam's apple)	Same as males. Tape level, not angled.
Waist	Circumference at the narrowest point of the torso, typically midway between the lowest rib and the top of the hip bone	Stand relaxed, measure at end of normal exhale. Tape level all the way around.
Hip	Circumference at the widest point of the hips/buttocks (greatest protrusion of the gluteal muscles)	Stand with feet together. Tape level and horizontal. Do not compress.

US Navy Body Fat Formula for Males

All measurements in inches. Height in inches.

Formula
Body Fat % = 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76

US Navy Body Fat Formula for Females

All measurements in inches. Height in inches.

Formula
Body Fat % = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387

Note: Use log₁₀ (common logarithm), not ln (natural logarithm). On most calculators, the "log" button is log₁₀ by default.

Example Calculation: Male

Measurement	Value
Height	70 inches (5'10")
Neck	15.5 inches
Waist	34 inches

Step 1: Calculate waist - neck

34 - 15.5 = 18.5

Step 2: Calculate log₁₀ values

log₁₀(18.5) = 1.2672

log₁₀(70) = 1.8451

Step 3: Plug into the formula

Body Fat % = 86.010 x 1.2672 - 70.041 x 1.8451 + 36.76

Body Fat % = 108.99 - 129.23 + 36.76

Body Fat % = 16.5%

Example Calculation: Female

Measurement	Value
Height	65 inches (5'5")
Neck	13 inches
Waist	29 inches
Hip	38 inches

Step 1: Calculate waist + hip - neck

29 + 38 - 13 = 54

Step 2: Calculate log₁₀ values

log₁₀(54) = 1.7324

log₁₀(65) = 1.8129

Step 3: Plug into the formula

Body Fat % = 163.205 x 1.7324 - 97.684 x 1.8129 - 78.387

Body Fat % = 282.67 - 177.03 - 78.387

Body Fat % = 27.3%

How to Take Accurate Measurements

The US Navy method lives or dies on measurement consistency. Small variations in tape placement or tension can shift your result by several percentage points. Follow these guidelines every time.

Measure at the same time of day. Morning measurements before eating and drinking produce the most consistent readings. Hydration, food intake, and even posture change throughout the day and affect circumference measurements.

Use the same tape measure every time. Different tapes can vary slightly in calibration. Cloth tapes can stretch over time. If you notice your tape becoming loose, replace it.

Keep the tape level and snug, not tight. The tape should sit flat against the skin at the same height all the way around. It should not indent the skin. Think "contact without compression."

Take each measurement two to three times. If two readings differ by more than half an inch, take a third and average the two closest. This matters more for the waist measurement, which has the biggest impact on the result.

Stand relaxed. Breathe normally. Do not suck in your stomach, flex, or hold your breath. Take the reading at the end of a normal exhale.

Measure the waist at the narrowest point, not at the belly button. This is the most common error with the US Navy method. The narrowest point of the torso is typically midway between the lowest rib and the top of the hip bone, which may be above or below the belly button depending on your anatomy.

For the neck, keep the tape just below the Adam's apple. Do not angle the tape. It should be level and horizontal.

Limitations of the US Navy Method

The US Navy formula estimates body fat from circumference ratios. This means it cannot distinguish between fat and muscle tissue the way caliper or DEXA methods can.

Muscular individuals may receive overestimated readings. A large waist circumference from core muscle mass will produce the same result as a large waist circumference from fat, even though the body composition is very different.

Very lean individuals may receive underestimated readings. At low body fat levels, the circumference ratios become less reliable predictors of actual fat mass.

People who carry fat primarily in unmeasured areas (such as the legs or upper arms) may see less accurate results, since the formula only measures the neck, waist, and (for females) hip.

For most people tracking general body composition trends, these limitations do not significantly diminish the method's usefulness. If you need more precision, a caliper-based method like the Jackson-Pollock 7-site or Durnin-Womersley formula will provide improved accuracy.

How the US Navy Method Compares to Other Formulas

Method	Equipment	Best For
US Navy (this article)	Tape measure only	Most accessible, no equipment, solo measurement
JP 3-Site	Calipers	Quick caliper estimate, beginners
JP 4-Site	Calipers	Same sites both genders, good accuracy
JP 7-Site	Calipers	Most comprehensive JP method
Durnin-Womersley	Calipers	Broad age range (16-72), age-specific equations
Yuhasz	Calipers	Athletes and highly fit individuals
Parillo	Calipers	Most measurement sites (9), simplest formula

Supporting Your Body Composition Goals

The US Navy method is the easiest way to start tracking your body fat. It takes five minutes, costs nothing, and gives you a baseline to measure against. Pairing consistent tracking with the right nutritional support helps you turn data into progress.

FitProbio+ features HOWARU Shape Bifidobacterium animalis subsp. lactis B420, a probiotic strain shown to assist with healthy body composition by supporting gut barrier function and promoting less calorie consumption. Each capsule is delivered in DRcaps gastro-resistant capsules and sealed in nitrogen-purged blister packs for stability.

FitFast combines berberine with InSea2, a blend of polyphenols derived from sustainably harvested brown seaweed. Formulated to support healthy blood glucose levels and a healthy glycemic response to food.

FitFight contains key amino acids (5-HTP, DL-Phenylalanine, L-Tyrosine, L-Glutamine) alongside chromium to support the biosynthesis of neurotransmitters involved in appetite control and mood. Chromium is present to support healthy glucose metabolism and food intake regulation.

Conclusion

The US Navy body fat formula is not the most precise method available, and it does not pretend to be. What it is, is the most accessible. A tape measure, two or three circumference readings, your height, and a calculator. That is the entire barrier to entry.

For many people, the US Navy method is the right starting point. It gives you a body fat estimate you can track over time, and it costs nothing. If your results motivate you to pursue more precision, caliper-based methods like Jackson-Pollock 3-site or Durnin-Womersley are natural next steps. And if you want the highest accuracy available, our guide to DEXA scans covers the gold standard in body composition analysis.

Start with what you have. A tape measure is enough.