Body Fat Calculator

Calculate your body fat percentage using the Navy method or BMI-based estimation

Body Measurements

Quick Examples

Enter Your Measurements

Select a calculation method, enter your body measurements, and get your estimated body fat percentage.

About Body Fat Calculation

U.S. Navy Method

The U.S. Navy method uses circumference measurements (waist, neck, and hip for women) to estimate body fat percentage. It is a practical field method commonly used in military and fitness settings.

BMI-Based Method

The BMI-based method uses your Body Mass Index along with age and sex to estimate body fat. While convenient, it is less accurate than the Navy method for athletic or muscular individuals.

Limitations

Both methods are estimates and can be affected by factors like muscle mass, bone density, and body shape. For the most accurate body composition analysis, consider DEXA scans or hydrostatic weighing.

Authoritative sources and references

The official standards, guidelines, and research behind this calculator's methodology.

Wikipedia — Body fat percentage

Body-fat percentage reference ranges and the measurement methods behind each estimate.

NIDDK — Weight Management

The U.S. National Institute of Diabetes and Digestive and Kidney Diseases hub for weight-management evidence.

Body Fat Calculator FAQ

Which method is more accurate?

The U.S. Navy method is generally more accurate than the BMI-based method because it uses actual body circumference measurements. However, both are estimates and less precise than clinical methods like DEXA scans.

What is a healthy body fat percentage?

For men, a healthy range is typically 14-17% (fitness level) to 18-24% (acceptable). For women, 21-24% (fitness) to 25-31% (acceptable). Essential fat levels (2-5% men, 10-13% women) are the minimum needed for basic physiological function.

How do I measure my waist and neck correctly?

Measure your waist at the navel level, standing relaxed. Measure your neck just below the larynx (Adam's apple) with the tape sloping slightly downward at the front. For women, measure hips at the widest point. Use a flexible tape measure and keep it snug but not tight.

How accurate is the Navy method compared to DEXA?

DEXA scans are the reference standard. The Navy circumference equations typically land within about 3–4 percentage points of DEXA when measurements are taken carefully — far better than no estimate, but not clinical-grade. The dominant error source is tape technique, not the formula.

Why do the Navy and BMI methods give me different numbers?

They measure different things: the Navy method models body shape from waist, neck, and hip circumferences, while the BMI-based estimate only knows height versus weight and assumes an average build. For muscular or very lean people the circumference method is usually more informative; the two agreeing closely suggests an average body composition.

How often should I remeasure my body fat?

Every 2–4 weeks, at the same time of day and with the same tape placement. Real body composition changes slowly — a few tenths of a percentage point per week at best — so daily readings mostly track water and gut content. Judge progress by the trend line, not single readings.

Understanding Body Fat: Formulas, Ranges and Measurement

How the Navy and BMI methods work, what the results mean, and how to measure consistently.

The U.S. Navy circumference method

The Navy method estimates body fat from three tape measurements — height, neck and waist (plus hip for women) — using equations published by the U.S. Navy in 1984 from the research of Hodgdon and Beckett. For men in centimetres: body fat % = 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. For women: 495 / (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450.

Because it tracks where fat actually accumulates (the waist), the Navy method is markedly better than weight-based estimates: validation studies against hydrostatic weighing report typical errors of about 3 percentage points for lean to average builds. Accuracy depends almost entirely on measuring the same spots the same way every time, which is why consistent technique matters more than the tape itself.

The BMI-based estimate: fast but rough

The BMI method uses the Deurenberg equation: body fat % ≈ 1.20 × BMI + 0.23 × age − 16.2 for men and − 5.4 for women. It needs nothing but height, weight, age and sex, which makes it useful when you have no tape measure at hand.

The trade-off is precision: BMI cannot tell muscle from fat, so the formula systematically overestimates body fat in muscular people and underestimates it in people with low muscle mass ("normal weight obesity"). Treat its output as a rough screening number and prefer the Navy method whenever you can take circumference measurements.

What the results mean

Body fat percentage categories follow the ranges popularised by the American Council on Exercise. The percentages are relative to total body weight:

  • Essential fat: 2–5% for men, 10–13% for women — the minimum needed for basic physiology.
  • Athletes: 6–13% for men, 14–20% for women.
  • Fitness: 14–17% for men, 21–24% for women.
  • Average: 18–24% for men, 25–31% for women.
  • Above average body fat: more than 25% for men, 32% for women.

How to measure for consistent results

Circumference measurements respond to technique more than most people expect, so follow a fixed routine:

  • Measure in the morning, after the bathroom and before eating or drinking, when the abdomen is least distended.
  • Men: measure the waist horizontally at the level of the navel; women: at the narrowest point of the abdomen.
  • Measure the neck just below the larynx, shoulders relaxed and without flaring the neck.
  • Keep the tape snug but not compressing the skin, and take each measurement two or three times, using the average.
  • Track the trend week over week rather than judging a single reading — measurement noise of ±1% is normal.

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The circumference mode implements the classical body-density estimate associated with Hodgdon–Beckett (1984), followed by the Siri 495/density − 450 conversion, using centimeters. It is not a certification of current Navy or Army eligibility. The BMI mode uses the Deurenberg adult estimate (1991): 1.20×BMI + 0.23×age − 10.8×sex − 5.4 (sex=1 for male, 0 for female). These are population models, not direct body-fat measurements or medical diagnoses. Without weight, fat/lean masses are not calculated.

Use the measurement procedure associated with the chosen model. For the classical circumference method: height without shoes, neck below the larynx, male abdomen at the navel, female natural waist and widest hip. Keep the tape level without compressing skin; repeat measurements. Select centimeters or inches for height and circumferences. Inches are converted using exactly 2.54 cm per inch; weight remains kilograms. Age is restricted to adults; implausible model outputs and non-positive logarithm inputs are rejected.

Army University Press: body composition policy