Body Fat Percentage Calculator
Example 1
A 30-year-old woman with a height of 1.63 m and weight of 58 kg wants to estimate her body fat percentage.
Solution
First calculate her BMI: BMI = 58 / (1.63 × 1.63) = 58 / 2.6569 = 21.83 kg/m².
The American Council on Exercise classifies this as the fitness range for women (21–24%).
Answer
27.9% body fat, which falls in the healthy fitness range for women. This method provides a quick estimate, but circumference-based methods such as the US Navy equation offer greater accuracy for individual assessment.
Source: Deurenberg et al., International Journal of Obesity, 1991
Example 2
A 40-year-old man with a height of 178 cm, neck circumference of 40 cm, and waist circumference of 88 cm wants to estimate his body fat percentage using the US Navy method.
Solution
Apply the US Navy formula for men: Body Fat % = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76.
The American Council on Exercise classifies this as the acceptable/fitness range for men (14–17%).
Answer
20.4% body fat, which falls in the acceptable/fitness range for men. This method is widely used by military and fitness professionals because it requires only a tape measure and yields results comparable to hydrostatic weighing within a 3.5% error margin.
Source: US Navy Body Composition Assessment, Department of Defense
Example 3
A 30-year-old man has a neck circumference of 38 cm and a waist circumference of 85 cm. He is 1.75 m tall and weighs 78 kg. Estimate his body fat percentage using the US Navy method and determine his category per ACE guidelines.
Solution
Waist - neck = 85 - 38 = 47 cm.
Body Density = 1.032 - 0.190 × log10(47) + 0.154 × log10(175) = 1.032 - 0.190 × 1.672 + 0.154 × 2.243 = 1.032 - 0.318 + 0.345 = 1.059 g/mL.
Body Fat % = (495/1.059 - 450) = 467.4 - 450 = 17.4%.
Answer
Estimated body fat: 17.4%. According to ACE guidelines, 14–17% is the "fitness" category for men. His fat mass would be 78 × 0.174 = 13.6 kg, and lean mass 78 – 13.6 = 64.4 kg.
Source: US Navy Body Composition Assessment, Hodgdon & Beckett, Naval Health Research Center, 1984
Example 4
A 40-year-old woman has neck circumference 32 cm, waist circumference 74 cm, and hip circumference 92 cm. She is 1.63 m tall and weighs 65 kg. Estimate her body fat percentage.
Solution
Waist + hip - neck = 74 + 92 - 32 = 134 cm.
Body Density = 1.295 - 0.350 × log10(134) + 0.221 × log10(163) = 1.295 - 0.350 × 2.127 + 0.221 × 2.212 = 1.295 - 0.744 + 0.489 = 1.040 g/mL.
Body Fat % = (495/1.040 - 450) = 476.0 - 450 = 26.0%.
Answer
Estimated body fat: 26.0%. ACE guidelines classify 25–31% as the "fitness" range for women. Her fat mass is 65 × 0.26 = 16.9 kg, and lean mass is 65 – 16.9 = 48.1 kg.
Source: US Navy Body Composition Assessment, Hodgdon & Beckett, Naval Health Research Center, 1984
Published:
Updated:
References
- [1]Naval Health Research Center, San Diego, Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height., 1984. https://pubmed.ncbi.nlm.nih.gov/6714674
- [2]American Council on Exercise, American Council on Exercise - Body Fat Percentage Categories. https://www.acefitness.org/resources/everyone/blog/6743/ace-reveals-new-body-fat-percentage-chart
- [3]CDC, Centers for Disease Control and Prevention - Body Composition Assessment. https://www.cdc.gov/healthyweight/assessing/index.html
Glossary
- Body fat percentage – The proportion of total body mass that consists of adipose tissue, expressed as a percentage of total weight.
- Essential fat – The minimum amount of body fat required for normal physiological function, found in bone marrow, organs, and cell membranes.
- Storage fat – Fat accumulated in adipose tissue as an energy reserve, divided into subcutaneous and visceral fat.
- Subcutaneous fat – Fat stored directly under the skin that provides insulation, energy storage, and cushioning for internal organs.
- Visceral fat – Fat stored deep inside the abdominal cavity surrounding the liver, pancreas, and intestines, linked to metabolic disease.
- Lean body mass – The total mass of the body minus fat mass, including muscle, bone, organs, connective tissue, and body water.
- Skinfold calipers – A handheld device used to measure subcutaneous fat thickness at specific body sites for body composition estimation.
- Bioelectrical impedance analysis (BIA) – A method that estimates body composition by measuring the resistance of body tissues to a small electrical current.
- DEXA scan – Dual-energy X-ray absorptiometry, a clinical gold standard for measuring bone density, fat mass, and lean mass.
- US Navy circumference method – A validated anthropometric technique using neck, waist, and hip circumference measurements to estimate body fat percentage.
How to Use?
- 1
Select your biological sex
Choose male or female from the dropdown. The US Navy method uses different formulas for each sex, and the hip circumference input appears automatically for female users.
- 2
Enter your body weight (optional)
Enter your weight in kilograms, pounds, or stone. This is optional — the body fat estimate itself does not require weight. If provided, the calculator also displays your fat mass and lean mass.
- 3
Enter your height and circumference measurements
Type your height and your neck, waist, and (for women) hip circumferences. Use the unit dropdowns to switch between centimetres and inches. Follow the measurement technique described in the guide below for consistent results.
- 4
Review your body fat percentage and category
Press Calculate to see your estimated body fat percentage, category, and status indicator. The colour-coded scale shows where your result falls relative to population ranges. If you entered weight, the fat mass and lean mass values appear below.
- 5
Track your progress over time
Record your body fat percentage alongside the date. Take measurements at the same time of day, using the same technique, once per month. A downward trend confirms fat loss; a stable trend confirms maintenance. Recalculate after every session to update the visual scale.
Frequently Asked Questions
The scale cannot distinguish between fat loss and muscle gain. If you lose 2 kg of fat and gain 2 kg of muscle, your weight stays the same but your body composition improves dramatically. Body fat percentage captures this change. It also provides a more accurate assessment of health risk because excess body fat (especially visceral fat), not excess weight per se, drives metabolic disease. Two people of the same weight can have completely different health profiles depending on their body fat percentage.
Monthly or quarterly tracking is recommended to monitor trends. Body fat changes slowly — a realistic rate of fat loss is 0.5–1% per month for most people. Measuring weekly introduces noise from hydration changes, food intake, and menstrual cycle phases, which can obscure the real trend. Measure at the same time of day (morning preferred), on the same day of the week, using the same technique and tape. Record each result and focus on the three-month trend rather than any single reading.
The US Navy method has a standard error of estimate of approximately 3.5%, meaning about two-thirds of individuals will have a true body fat percentage within 3.5 points of the estimate. The correlation with hydrostatic weighing (the gold standard) is r = 0.90 in the validation population. Accuracy depends heavily on correct tape placement and consistent technique. It is less accurate for extremely lean individuals, elderly adults, and people with unusual fat distribution patterns. Among field methods that require no special equipment, it is one of the most accurate available.
For men, 10–20% body fat is generally considered healthy; for women, 18–28%. Athletes often have lower ranges: 6–13% for men and 14–20% for women. Essential fat below 5% for men or 10% for women can be dangerous, causing hormonal disruption, immune impairment, and bone density loss. The optimal range depends on your age, activity level, and individual health profile. Use the ACE categories provided on this page as a reference, but discuss your specific target with a healthcare provider.
Yes. For consistent results, measure at the same time of day, preferably in the morning before eating or drinking and after emptying your bladder. Waist circumference can vary by 1–3 cm between morning and evening due to food intake and digestive gas. Avoid measuring after exercise, after a large meal, or during the evening. Consistent timing is more important than the absolute accuracy of any single measurement because the trend over time is what matters.
DEXA (dual-energy X-ray absorptiometry) is the clinical gold standard for body composition measurement, with an accuracy of about 1–2%. It measures fat mass, lean mass, and bone mineral density separately and can distinguish between subcutaneous and visceral fat. However, DEXA requires specialised equipment, costs $50–200 per scan, and involves low-dose radiation. The US Navy method has about 3.5% accuracy, costs nothing, and can be done at home with a tape measure. For regular tracking of body composition changes, the US Navy method is practical and sufficiently accurate. For a one-time baseline or clinical assessment, DEXA provides more detail.
Body fat estimation during pregnancy is not reliable because the formula does not account for the weight of the fetus, placenta, amniotic fluid, and increased blood volume. Waist circumference also changes significantly during pregnancy independent of body fat changes. Pre-pregnancy body fat percentage can be a useful baseline for tracking post-partum recovery, but measurements taken during pregnancy itself will not produce meaningful results. Wait until at least 6–8 weeks after delivery to resume body composition tracking.
The relationship between circumference measurements and body density is not linear. As body fat increases, the relationship between waist circumference and density changes at a decreasing rate. Logarithmic transformations linearise this relationship, allowing standard regression techniques to produce accurate predictions. This is the same statistical approach used in skinfold prediction equations (Jackson-Pollock, Durnin-Womersley) and in many other anthropometric prediction models. The base-10 logarithms used in the US Navy equations are simple to compute and produce the best fit with measured body density in the validation population.
Dehydration reduces total body water, which decreases soft tissue volume and can reduce waist and neck circumferences by 0.5–2 cm. This leads to a falsely low body fat estimate. Conversely, overhydration (common after high-carb meals or intense exercise) can increase circumferences and produce a falsely high estimate. The US Navy method is a circumference-based technique and is less affected by hydration than bioelectrical impedance (BIA), which measures body water directly. For most reliable results, maintain normal hydration and measure at the same time each day.
Essential fat is the fat required for normal physiological function, found in bone marrow, organs, cell membranes, and the central nervous system. It makes up about 3% of body mass in men and 12% in women (the higher percentage in women is due to sex-specific fat deposits). Storage fat is the fat accumulated in adipose tissue as an energy reserve, subdivided into subcutaneous fat (under the skin) and visceral fat (around internal organs). Body fat percentage above essential levels consists of storage fat. The ACE categories on this page define the ranges: essential fat levels are the minimum for health, athletes and fitness ranges include moderate storage fat, and the obese range indicates excess storage fat that increases disease risk.
Body fat percentage is more informative than BMI for individual health assessment because it directly measures adiposity rather than inferring it from weight and height. However, both metrics have value. BMI is the standard screening tool at the population level and is widely recognised by health organisations, making it useful for communicating with healthcare providers. Body fat percentage fills the gap that BMI leaves: it resolves the ambiguity of high-BMI-but-lean (athletes) and normal-BMI-but-high-fat (normal-weight obesity). The most comprehensive approach is to calculate both. Use this body fat calculator alongside the BMI calculator on this site for a complete picture.
Body fat below the essential minimum (5% for men, 14% for women) carries significant health risks. In men, very low body fat suppresses testosterone production, reduces libido, impairs immune function, and increases the risk of stress fractures and osteoporosis. In women, the consequences include amenorrhea (loss of menstrual cycle), infertility, reduced bone density, and increased risk of the Female Athlete Triad. Very low body fat also impairs thermoregulation, reduces energy availability for training and daily activities, and increases the risk of illness and injury. For these reasons, the essential fat category is flagged as a warning on this calculator.
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