Body Fat Calculator

Use a flexible, non-stretch tape and measure against bare skin, keeping the tape level and snug without compressing the skin. Measure the neck just below the larynx (Adam's apple), sloping slightly downward toward the front. For men, measure the waist horizontally at the navel; for women, at the narrowest point of the natural waist. Women also measure the hips at their widest point. Stand relaxed, breathe out normally, and take each measurement two or three times to get a consistent number.

Body Fat, Overweight, and Obesity

Body fat, or adipose tissue, is not just stored energy. It cushions organs, insulates the body and acts as an endocrine organ that releases hormones such as leptin, which helps regulate appetite, and adiponectin, which affects how the body handles sugar. A certain amount, called essential fat, is required for normal function. It is found in nerves, bone marrow, cell membranes and around organs. Women need considerably more essential fat than men, roughly 10% to 13% of body weight compared with 2% to 5%, largely because of tissue related to reproduction and hormones.

Most body fat is white fat stored under the skin (subcutaneous fat) and around the internal organs of the abdomen (visceral fat). Visceral fat is the more harmful of the two: it is more metabolically active, releases fatty acids and inflammatory substances directly to the liver, and is closely linked to insulin resistance, high blood pressure and heart disease. A large waist is a practical sign of excess visceral fat. Brown fat, which burns energy to produce heat, is present in small amounts in adults.

Overweight and obesity mean carrying excess body fat to a degree that may harm health. In everyday practice they are defined using BMI: the World Health Organization classes adults with a BMI of 25 or more as overweight and 30 or more as obese. BMI is convenient but indirect, because it cannot tell fat from muscle. Body fat percentage describes body composition more directly. There is no universal cut-off, but fitness organizations such as the American Council on Exercise generally consider more than about 25% body fat in men and 32% in women to fall in the obese range.

Body fat changes with age. Even at a stable weight, adults tend to lose muscle and gain fat over the decades, which is why ideal ranges rise slightly with age. The WHO estimated that in 2022 about 2.5 billion adults worldwide were overweight, and 890 million of them were living with obesity.

Potential Complications of Excess Body Fat

Carrying too much body fat, especially visceral fat, raises the risk of a long list of health problems. According to the CDC and the National Institutes of Health, these include:

• Type 2 diabetes, through insulin resistance
• High blood pressure, high LDL cholesterol, low HDL cholesterol and high triglycerides
• Coronary heart disease, heart failure and stroke
• Non-alcoholic fatty liver disease
• Several cancers, including colorectal, endometrial, kidney, liver and post-menopausal breast cancer
• Sleep apnea and other breathing problems
• Osteoarthritis, particularly of the knees and hips, and gout
• Gallbladder disease
• Fertility problems and complications in pregnancy, such as gestational diabetes and preeclampsia
• Depression, anxiety and reduced quality of life

The good news is that the risks respond to change. Losing 5% to 10% of body weight can lower blood pressure, improve blood sugar and cholesterol, and reduce liver fat. Regular physical activity reduces visceral fat even when total weight changes little. Very low body fat carries risks too: dropping below essential levels can disrupt hormones, stop menstrual periods, weaken bones and impair immunity.

Measuring Body Fat Percentage

There are many ways to estimate body fat, and they trade accuracy against cost and convenience. None of them measures fat directly in a living person, so every method carries some error.

The U.S. Navy method used here was developed by Hodgdon and Beckett at the Naval Health Research Center in the 1980s. It predicts body fat from height and neck and waist circumferences, plus hip circumference for women, using equations fitted to laboratory measurements. It needs only a tape measure and is typically within about 3 to 4 percentage points of reference methods, though it can be less accurate for very muscular or very heavy people.

The BMI method uses an equation published by Deurenberg and colleagues in 1991 that estimates body fat from BMI, age and sex. It needs no tape measurements, but it inherits BMI's inability to distinguish muscle from fat, so it is best treated as a rough cross-check.

Other common methods include:

• Skinfold calipers: a trained tester pinches folds of skin and fat at three to seven sites and converts the thicknesses with equations such as those of Jackson and Pollock. Accuracy depends heavily on the tester's skill.
• Bioelectrical impedance analysis (BIA): bathroom scales and handheld devices send a weak current through the body, which travels more easily through water-rich lean tissue than through fat. Results shift with hydration, meals and exercise, so measure under the same conditions each time.
• Dual-energy X-ray absorptiometry (DEXA): a low-dose X-ray scan that separates fat, lean tissue and bone and shows where fat is distributed. It is one of the most accurate methods available but requires specialist equipment.
• Hydrostatic (underwater) weighing: compares weight on land with weight while fully submerged, since fat is less dense than lean tissue. Long considered a reference standard.
• Air displacement plethysmography: a sealed chamber such as the Bod Pod measures body volume from the air displaced, working on the same density principle without immersion.

Men: BF% = 495 ÷ (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450 Women: BF% = 495 ÷ (1.29579 − 0.35004·log₁₀(waist + hip − neck) + 0.22100·log₁₀(height)) − 450

waist, neck, hip, height

circumferences and height in centimeters

BMI method (adults): BF% = 1.20 × BMI + 0.23 × age − 16.2 for men, or − 5.4 for women. For under-18s: 1.51 × BMI − 0.70 × age − 2.2 (boys) or + 1.4 (girls).

Frequently asked questions

Sources

• CDC – Healthy Weight and Growth
• NIH NHLBI – Overweight and Obesity
• WHO – Obesity and overweight
• American Council on Exercise