How to Calculate Body Fat Percentage (5 Methods)

TL;DR Body fat percentage is the proportion of your total body weight that consists of fat tissue, and you can estimate it at home using the U.S. Navy circumference method (tape measure + a simple formula), skinfold calipers, or a bioelectrical impedance scale. For clinical accuracy, DEXA scans and hydrostatic weighing are the gold standards. Below, we walk through all five methods with step-by-step instructions so you can pick the one that fits your budget and goals.

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What Is Body Fat Percentage?

Body fat percentage is the share of your total body mass made up of adipose (fat) tissue, expressed as a percentage. If you weigh 180 pounds and have 36 pounds of fat, your body fat percentage is 20%. Unlike BMI, which only considers height and weight, body fat percentage distinguishes between fat mass and lean mass (muscle, bone, water, organs). Two people with identical BMIs can have very different body compositions — one may carry significantly more muscle while the other carries more fat.

Tracking body fat percentage matters because it gives you a clearer picture of your health than the number on a scale. Excess visceral fat — the fat stored around internal organs — is linked to increased risk of type 2 diabetes, cardiovascular disease, and metabolic syndrome, regardless of overall body weight. On the other hand, having too little body fat can disrupt hormone production, weaken your immune system, and impair organ function.

Healthy Body Fat Ranges

Category	Men	Women
Essential fat	2–5%	10–13%
Athletes	6–13%	14–20%
Fitness	14–17%	21–24%
Average	18–24%	25–31%
Above average	25%+	32%+

Source: American Council on Exercise (ACE) body fat classification chart.

These ranges differ between men and women because women carry more essential fat to support reproductive function and hormone regulation.

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Method 1: U.S. Navy Circumference Method (Tape Measure)

The U.S. Navy body fat formula uses a few body measurements and basic math to estimate body fat percentage. It was developed for military fitness assessments and remains one of the most accessible methods — all you need is a flexible tape measure.

What You Measure

• Neck circumference — measured just below the larynx (Adam’s apple), tape sloping slightly downward at the front.
• Waist circumference — measured at the navel for men, at the narrowest point of the torso for women.
• Hip circumference (women only) — measured at the widest point of the hips and buttocks.
• Height — standing, without shoes.

The Formula

For men:

[ \text{Body Fat %} = 86.010 \times \log_{10}(\text{waist} - \text{neck}) - 70.041 \times \log_{10}(\text{height}) + 36.76 ]

For women:

[ \text{Body Fat %} = 163.205 \times \log_{10}(\text{waist} + \text{hip} - \text{neck}) - 97.684 \times \log_{10}(\text{height}) - 78.387 ]

All measurements are in centimeters. If you measured in inches, multiply each measurement by 2.54 before plugging into the formula.

Worked Example (Male)

• Height: 178 cm (5’10”)
• Neck: 38 cm
• Waist: 88 cm

Step 1: Waist minus neck = 88 - 38 = 50 cm Step 2: log10(50) = 1.6990 Step 3: log10(178) = 2.2504 Step 4: 86.010 x 1.6990 = 146.13 Step 5: 70.041 x 2.2504 = 157.61 Step 6: 146.13 - 157.61 + 36.76 = 25.28%

Accuracy

The Navy method is accurate to within 3-4% of DEXA for most people. It tends to overestimate body fat in very muscular individuals and underestimate it in those with high visceral fat but small waist measurements. For ongoing tracking, it is reliable as long as you measure at the same spots each time.

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Method 2: Skinfold Calipers

Skinfold testing uses a handheld caliper to pinch and measure the thickness of subcutaneous fat at specific body sites. The measurements are plugged into a population-specific equation (most commonly the Jackson-Pollock 3-site or 7-site formulas) to estimate total body fat.

How to Do a 3-Site Skinfold Test (Jackson-Pollock)

Men — measure these three sites:

1. Chest — a diagonal fold halfway between the armpit crease and the nipple.
2. Abdomen — a vertical fold 2 cm to the right of the navel.
3. Thigh — a vertical fold on the front of the thigh, midway between the hip and knee.

Women — measure these three sites:

1. Triceps — a vertical fold on the back of the upper arm, midway between the shoulder and elbow.
2. Suprailiac — a diagonal fold just above the iliac crest (hip bone).
3. Thigh — same as men.

Steps

1. Take each measurement on the right side of the body.
2. Pinch the skin, pull it away from the muscle, and place the caliper jaws about 1 cm below your fingers.
3. Wait 2 seconds, then read the measurement in millimeters.
4. Repeat each site twice and average the readings.
5. Sum all three site averages to get your “sum of skinfolds” value.
6. Use the Jackson-Pollock body density formula, then convert density to body fat percentage with the Siri equation:

[ \text{Body Fat %} = \left(\frac{495}{\text{Body Density}}\right) - 450 ]

Accuracy

When performed by an experienced tester, calipers are accurate to within 3-4%. Self-testing introduces more error, especially at hard-to-reach sites. Calipers cost between $10 and $30 and are a good investment if you plan to track progress monthly.

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Method 3: Bioelectrical Impedance Analysis (BIA)

Bioelectrical impedance analysis sends a weak, painless electrical current through your body. Fat tissue conducts electricity poorly compared to water-rich lean tissue, so the device measures resistance (impedance) and uses it to estimate your body composition.

How to Use a BIA Device

1. Step onto a BIA-enabled scale (like those from Withings, Renpho, or Tanita) with bare, dry feet.
2. Enter your age, sex, and height if prompted.
3. Stand still for 5-10 seconds while the device takes the reading.
4. Read your body fat percentage from the display or companion app.

Some models also have handheld grips that send the current through your upper body for a full-body reading.

Tips for Consistent Results

• Measure at the same time each day — first thing in the morning, after using the bathroom, before eating or drinking.
• Avoid measuring after intense exercise, a sauna, or alcohol consumption, all of which alter hydration and skew results.
• Stay consistent with hydration. Drinking significantly more or less water than usual will change the reading.

Accuracy

Consumer BIA scales are accurate to within 5-8% compared to DEXA. They are better for tracking trends over weeks and months than for pinpointing your exact body fat percentage on any single day. Hydration level is the biggest source of error.

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Method 4: DEXA Scan (Dual-Energy X-Ray Absorptiometry)

DEXA is considered one of the two gold-standard methods for measuring body composition. The scan uses two low-dose X-ray beams at different energy levels to differentiate between bone, lean tissue, and fat tissue.

What to Expect

1. You lie on a padded table for 10-20 minutes.
2. A mechanical arm passes over your body, emitting low-level X-rays.
3. The machine produces a full-body map showing fat distribution, lean mass by region, and bone mineral density.
4. A technician or physician reviews the report with you.

Cost and Availability

DEXA scans typically cost $75-$200 per session at radiology clinics, university research labs, or sports performance centers. Some gyms and health clinics offer them as well. Insurance rarely covers DEXA for body composition alone (though it may cover it for bone density screening).

Accuracy

DEXA has a test-retest accuracy of about 1-2%, making it the most precise widely available method. It also reveals regional fat distribution, so you can see if you carry more fat in your trunk versus your limbs — information the other methods cannot provide.

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Method 5: Hydrostatic (Underwater) Weighing

Hydrostatic weighing determines body density by comparing your weight on land to your weight submerged in water. Since fat is less dense than lean tissue, a person with more body fat will weigh relatively less underwater.

How It Works

1. You are weighed on a standard scale (dry weight).
2. You sit in a specialized chair attached to a scale, submerged in a warm water tank.
3. You exhale as much air as possible and remain still while the underwater scale records your weight.
4. The procedure is repeated 2-3 times, and the highest underwater weight is used.
5. Body density is calculated from the difference between dry weight and underwater weight, accounting for residual lung volume.
6. The Siri equation converts density to body fat percentage.

Accuracy

Hydrostatic weighing is accurate to within 1-2%, comparable to DEXA. The main limitation is accessibility — it requires specialized equipment typically found only at universities and sports science facilities. The process can also be uncomfortable for people who are not confident in water or have difficulty exhaling fully.

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Comparing All Five Methods

Method	Cost	Accuracy (vs DEXA)	Convenience	Best For
Navy tape measure	Free (tape measure)	±3–4%	Do it at home anytime	Budget-friendly baseline tracking
Skinfold calipers	$10–$30	±3–4% (trained tester)	At home or gym	Monthly progress tracking
BIA scale	$25–$200	±5–8%	Step on daily	Trend monitoring over time
DEXA scan	$75–$200/session	±1–2% (gold standard)	Clinic appointment	Accurate baseline + regional data
Hydrostatic weighing	$50–$150/session	±1–2%	Lab appointment	Research-grade accuracy

For most people, the Navy method or a BIA scale provides enough accuracy to track progress. Reserve DEXA scans for quarterly or biannual checkpoints if you want precise data.

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How BMI Relates to Body Fat

BMI (Body Mass Index) divides your weight in kilograms by your height in meters squared. It is a screening tool, not a body composition measurement. A BMI of 25–29.9 is classified as “overweight,” but that classification does not account for whether the extra weight is muscle or fat.

Research published in the International Journal of Obesity found that roughly 30% of people classified as “normal weight” by BMI actually had excess body fat (a condition called normal-weight obesity), while many athletes classified as “overweight” had body fat percentages in the fitness or athletic range.

Use our free BMI Calculator to get your BMI as a starting reference point. Then pair it with one of the body fat methods above for a more complete picture.

If you are also working on weight management, check out our Calorie Deficit Calculator to find a safe daily calorie target based on your activity level and goals.

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How to Lower Your Body Fat Percentage

Reducing body fat while preserving lean mass requires a combination of a moderate calorie deficit, adequate protein intake, and resistance training.

1. Create a Moderate Calorie Deficit

A deficit of 300–500 calories per day is enough to lose roughly 0.5–1 pound per week without significant muscle loss. Going much below that increases the risk of metabolic adaptation and muscle catabolism. Use a calorie calculator to find your maintenance calories, then subtract 300–500.

2. Eat Enough Protein

Research consistently shows that consuming 0.7–1.0 grams of protein per pound of body weight per day helps preserve lean mass during a deficit. Protein also has the highest thermic effect of any macronutrient, meaning your body uses more energy digesting it.

3. Lift Weights

Resistance training signals your body to hold onto muscle tissue. Aim for 3–4 sessions per week targeting all major muscle groups. Compound movements — squats, deadlifts, bench press, rows — give you the most stimulus per unit of time.

4. Get Enough Sleep

Sleep deprivation increases cortisol and ghrelin (the hunger hormone) while decreasing leptin (the satiety hormone). Studies show that people who sleep fewer than 6 hours per night lose more lean mass and less fat mass during a calorie deficit compared to those who sleep 7–9 hours.

5. Be Patient

Losing body fat while keeping muscle is slower than just losing weight. Aim for 0.5–1% body fat reduction per month. Measure your body fat using the same method, at the same time of day, every 2–4 weeks to track real trends rather than daily fluctuations.

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FAQ

Q: What is body fat percentage? A: Body fat percentage is the proportion of your total body weight that is made up of fat tissue. It is calculated by dividing your fat mass by your total body mass and multiplying by 100. Unlike BMI, which only factors in height and weight, body fat percentage differentiates between fat and lean tissue, giving you a more accurate picture of your body composition.

Q: Is this tool free to use? A: Yes. Our BMI Calculator is completely free, runs entirely in your browser, and never sends your data to any server. Your measurements stay on your device. No account or signup is required.

Q: What is the most accurate way to measure body fat at home? A: The U.S. Navy circumference method (tape measure) and skinfold calipers are the most accurate at-home options, both within 3–4% of DEXA results when performed correctly. For tracking trends over time, consistency in how and when you measure matters more than the absolute accuracy of any single reading.

Q: How often should I measure my body fat percentage? A: Every 2–4 weeks is ideal for most people. Measuring more frequently introduces noise from hydration changes, food intake, and measurement error. If you use a BIA scale, weigh yourself daily but look at the 7-day or 14-day rolling average rather than any single reading.

Q: Can I have a healthy weight but unhealthy body fat percentage? A: Yes. This is called normal-weight obesity, or “skinny fat.” A person can have a BMI in the normal range (18.5–24.9) while carrying excess body fat and insufficient muscle mass. Studies estimate that 20–30% of normal-weight adults fall into this category. Measuring body fat percentage — not just weight or BMI — is the only way to identify it.

Q: What is the difference between body fat percentage and BMI? A: BMI is a ratio of weight to height (kg/m squared) that categorizes you as underweight, normal, overweight, or obese. It does not distinguish fat from muscle. Body fat percentage measures the actual proportion of fat in your body. A muscular person may have a high BMI but a low body fat percentage, while a sedentary person may have a normal BMI but a high body fat percentage.

Q: Does age affect body fat percentage? A: Yes. Body fat tends to increase with age even if weight stays the same, because people gradually lose muscle mass after age 30 (a process called sarcopenia). This is why maintaining resistance training and adequate protein intake becomes increasingly important as you get older.

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Callout

Check your BMI with our free BMI Calculator

Get your BMI in seconds, then use the Navy method above to estimate your body fat percentage for a more complete picture of your body composition.

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Additional Resources

• Calorie Deficit Calculator — Find out how many calories you need to eat to lose fat at a safe, sustainable rate.
• Calorie Calculator — Estimate your daily calorie needs based on your age, sex, weight, height, and activity level.
• Percentage Calculator — Convert between fractions, decimals, and percentages for any body composition math you need to do.

References:

1. American Council on Exercise. “ACE Body Fat Classification.” https://www.acefitness.org/education-and-resources/lifestyle/tools-calculators/percent-body-fat-calculator/
2. Hodgdon, J.A. & Beckett, M.B. “Prediction of percent body fat for U.S. Navy men and women from body circumferences and height.” Naval Health Research Center, Report No. 84-29.
3. Jackson, A.S. & Pollock, M.L. (1978). “Generalized equations for predicting body density of men.” British Journal of Nutrition, 40(3), 497-504.