Body Fat Percentage Calculator

Last updated: April 5, 2026

The Body Fat Percentage Calculator estimates your percentage body fat using the US Navy circumference method and compares it against ACE and ACSM healthy ranges for your sex and age. Body fat percentage tells you the fraction of your weight that is fat versus lean tissue — more actionable than BMI.

Calculator

Sex

Weightlbs

Heightin

Waist Circumferencein

Neck Circumferencein

Hip Circumferencein

Results

Body Fat

9.1

Fat Mass

lbs

Lean Mass

159

lbs

Fat Mass

7.3

Lean Mass

72.1

BMI

25.1

Results

Body Fat

9.1

Fat Mass

lbs

Lean Mass

159

lbs

Fat Mass

7.3

Lean Mass

72.1

BMI

25.1

Weight on a scale tells you your total mass. Body fat percentage tells you how much of that mass is working for you (muscle, bone, organs) versus how much is stored fat. Two people of identical height and weight can have body fat percentages 15% apart — with completely different metabolic health profiles. The body fat percentage calculator gives you this number from simple measurements and shows where you stand on evidence-based health and fitness ranges.

Body Fat Calculation: US Navy Method

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

Measurements in cm: waist at narrowest (men) or navel (women); neck below larynx; hips at widest (women). Use this online calculator for your result. The lean body mass calculator converts your percentage to absolute lean and fat mass in kg.

ACSM Body Fat Classification

Men (20–39): lean 8–19%; healthy 20–24%; overweight 25–29%; obese 30%+
Men (40–59): lean 11–21%; healthy 22–27%; overweight 28–32%; obese 33%+
Women (20–39): lean 21–32%; healthy 33–38%; overweight 39–43%; obese 44%+
Women (40–59): lean 23–33%; healthy 34–39%; overweight 40–44%; obese 45%+

Why Body Fat Matters Beyond BMI

"Normal weight obesity" — normal BMI with excess body fat — affects approximately 20–30% of adults with BMI in the healthy range. These individuals have elevated insulin resistance, dyslipidemia, and cardiovascular risk despite appearing normal-weight by BMI. Body fat percentage catches this group. Conversely, athletes with BMI in the overweight range often have body fat percentages well within the healthy range — BMI misclassifies them as unhealthy when they are not. The complete picture: BMI for quick population screening + body fat % for body composition + waist circumference for fat distribution. The waist-to-hip ratio and health calculators complement this assessment.

Setting Body Fat Goals

Realistic rates of fat loss: 0.5–1% body fat per month is achievable with a sustained 300–500 kcal/day deficit combined with resistance training. Faster rates (above 1.5%/month) typically involve significant lean mass loss, counterproductive for most goals. Target a body fat percentage that is: within the healthy range for your age and sex; sustainable without chronic caloric restriction; compatible with maintaining adequate energy for work, exercise, and life. Consult a registered dietitian for a personalized body composition goal and timeline.

Visual Analysis

How It Works

Enter height, weight, neck circumference, waist circumference, and hip circumference (women). US Navy formulas compute body fat %. Fat mass (kg) = weight × BF%/100; lean mass = weight − fat mass. Result is classified against ACE/ACSM ranges by sex and age group: essential, athletic, fitness, average, or obese.

Understanding Your Results

For men, 6–13% is athletic, 14–17% is fitness level, 18–24% is acceptable, and above 25% is considered overweight. For women, 14–20% is athletic, 21–24% is fitness level, 25–31% is acceptable, and above 32% is considered overweight. Your lean mass number is particularly valuable — it represents the minimum weight you would be if you had zero body fat and serves as a baseline for calculating how much weight you'd need to lose to reach a target body fat percentage.

Worked Examples

Athletic male, 180 lbs, 5'10"

Inputs

gendermale

weight lbs180

height in70

waist in32

neck in16

hip in40

Results

body fat pct12.4

fat mass lbs22.3

lean mass lbs157.7

At 12.4% body fat, this man is in the athletic range. His lean mass of 157.7 lbs means losing 20 lbs of fat would bring him to roughly 6.5% body fat.

Average female, 145 lbs, 5'5"

Inputs

genderfemale

weight lbs145

height in65

waist in30

neck in13

hip in40

Results

body fat pct26.8

fat mass lbs38.9

lean mass lbs106.1

At 26.8% body fat, this woman falls in the acceptable range. Reaching 22% would require losing approximately 7 lbs of fat while maintaining lean mass.

Frequently Asked Questions

Healthy body fat ranges differ by sex and age. Using ACE standards — Men: 14–17% is 'fitness' level; 18–24% is 'acceptable' for most adults; above 25% is classified obese. Women: 21–24% is 'fitness' level; 25–31% is 'acceptable'; above 32% is obese. ACSM provides age-stratified ranges: men aged 20–39 are healthy at 8–19% (lean) to 20–24% (acceptable); women the same age are healthy at 21–32% (lean) to 33–38% (acceptable). Body fat naturally increases with age — a 55-year-old at 25% body fat is in a different relative category than a 25-year-old at 25%. Always evaluate body fat percentage in the context of your age, sex, fitness level, and health history with your healthcare provider.

BMI (Body Mass Index) is the ratio of weight to height squared — it has no units and does not measure body composition. Body fat percentage is the fraction of your total weight that is fat tissue. BMI cannot distinguish fat from muscle: a 90 kg, 180 cm bodybuilder with 8% body fat and a 90 kg, 180 cm sedentary person with 35% body fat both have a BMI of 27.8 ('overweight') — yet their body compositions and health risk profiles are completely different. Body fat percentage is more accurate for assessing individual metabolic health risk. BMI remains useful for population-level screening because it requires no measurements beyond height and weight. For individual health assessment, body fat percentage is the more meaningful metric.

The most practical home methods: US Navy circumference method (this calculator) — use a cloth tape measure to measure neck, waist, and hips; free and reasonably accurate (±3–4%); BIA smart scales (body composition scales with bioelectrical impedance) — easy but sensitive to hydration, time of day, and eating; accuracy ±3–5% under consistent conditions; skinfold calipers — inexpensive (USD 10–25) but require learning proper technique; Jackson-Pollock 3-site is most practical; accuracy ±3–5% with good technique. For home tracking purposes, the Navy method is the most reproducible without equipment investment. The key is using the same method consistently so trends are meaningful, even if the absolute value has some error.

Yes — body fat percentage naturally increases with age even at stable weight, primarily because lean muscle mass declines approximately 3–5% per decade after age 30 (sarcopenia). As muscle is lost and replaced by fat or simply lost without replacement, the fat fraction of total body weight rises. An individual who weighs the same at 55 as they did at 30 will have substantially higher body fat percentage at the older age. This is why body fat reference ranges are age-stratified — a 60-year-old at 27% body fat may be appropriately lean for their age, while the same percentage in a 25-year-old might indicate excess adiposity. Resistance training is the most effective intervention to slow age-related muscle loss and the accompanying rise in body fat percentage.

Normal weight obesity (NWO) refers to individuals who have a BMI in the 'normal' range (18.5–24.9) but elevated body fat percentage — typically defined as above 30% in men and above 35–38% in women. Prevalence estimates suggest NWO affects 20–30% of normal-weight adults. These individuals have higher rates of metabolic syndrome, insulin resistance, dyslipidemia, and cardiovascular risk compared to normal-weight people with normal body fat percentage — risks that BMI alone completely misses. NWO is most common in older adults and in people who are sedentary with low muscle mass. The only way to identify NWO is to measure body fat percentage directly — which is one of the strongest arguments for using body fat measurement alongside BMI in clinical and fitness assessment.

At a sustained caloric deficit of 500 kcal/day with resistance training: approximately 0.5 kg of fat per week (roughly 0.5–0.7% body fat/week for a 70–80 kg person). At 300 kcal/day deficit: approximately 0.3 kg/week. These rates assume the deficit comes primarily from fat rather than lean tissue — which requires adequate protein (1.6–2.2 g/kg body weight/day) and resistance training. More aggressive deficits increase lean mass loss disproportionately. Over a month: a realistic fat loss of 1–2 kg corresponds to approximately 1–2% body fat reduction in an average-sized adult. Body fat percentage also depends on lean mass changes — if you are gaining muscle while losing fat (body recomposition), body fat % can drop significantly even with modest weight loss.

Sources & Methodology

Hodgdon, J.A., Beckett, M.B. (1984). Prediction of percent body fat for US Navy men. NHRC Report 84-11. ACSM (2022). ACSM's Guidelines for Exercise Testing and Prescription, 11th ed. ACE (2009). Percent Body Fat Norms for Men and Women.

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How It Works

Understanding Your Results

Worked Examples

Athletic male, 180 lbs, 5'10"

Inputs

gendermale

weight lbs180

height in70

waist in32

neck in16

hip in40

Results

body fat pct12.4

fat mass lbs22.3

lean mass lbs157.7

At 12.4% body fat, this man is in the athletic range. His lean mass of 157.7 lbs means losing 20 lbs of fat would bring him to roughly 6.5% body fat.

Average female, 145 lbs, 5'5"

Inputs

genderfemale

weight lbs145

height in65

waist in30

neck in13

hip in40

Results

body fat pct26.8

fat mass lbs38.9

lean mass lbs106.1

At 26.8% body fat, this woman falls in the acceptable range. Reaching 22% would require losing approximately 7 lbs of fat while maintaining lean mass.

Frequently Asked Questions