How to Measure Body Fat Percentage

Body Fat Percentage Measurement Methods Compared

There are five main body fat percentage measurement methods in use today, each with a different balance of accuracy, cost, and convenience. The table below summarizes how they compare.

1. U.S. Navy Tape Method

Developed by Hodgdon and Beckett at the Naval Health Research Center in 1984^[1], the Navy method uses three to four body circumference measurements to estimate body fat percentage. It is the official method used by the U.S. Navy, Army, Marines, and Air Force for body composition assessment.

For men, you measure neck, waist, and height. For women, you add hip circumference because of differences in fat distribution. The formula uses the ratio of waist to neck (plus hip for women), adjusted for height, to predict body fat.

Accuracy: ±1–3% body fat. Clinical studies show good correlation with hydrostatic weighing and DEXA scans when measurements are taken correctly.

Best for: Most people. It is the best balance of accuracy, cost, and convenience for home measurement. Use our free body fat percentage calculator to apply the Navy formula to your measurements.

2. Skinfold Calipers

Skinfold calipers pinch the skin and underlying fat at specific body sites to measure subcutaneous fat thickness. The most common protocols use 3, 4, or 7 sites, and the sum of the folds is converted to a body fat estimate using equations like those developed by Jackson and Pollock^[2].

Common sites: Chest, abdomen, thigh, triceps, suprailiac (hip), subscapular (shoulder blade), and midaxillary (side of ribs).

Accuracy: ±3–4% body fat when measured by a trained practitioner. Accuracy drops significantly with inexperienced measurers because technique matters enormously.

Best for: People who have access to a trained practitioner (personal trainer, fitness coach). Self-measurement is possible but significantly less accurate because you cannot reach all sites consistently.

3. Smart Scales and Bioelectrical Impedance (BIA)

Bioelectrical impedance analysis sends a small, safe electrical current through the body. Fat resists the current more than muscle and water, so the device estimates body fat based on how the current travels. BIA is found in smart scales, handheld devices, and professional machines (like InBody).

Accuracy: ±3–5% body fat, but readings are highly sensitive to hydration status, recent meals, exercise, skin temperature, and time of day^[3]. Two readings taken hours apart can differ by several percent.

Best for: Tracking trends over time if you measure under consistent conditions (same time of day, same hydration status, before eating or exercising). Not recommended for precise single-point readings.

4. DEXA Scan

DEXA (dual-energy X-ray absorptiometry) is considered the clinical gold standard for body composition measurement^[4]. It uses two low-dose X-ray beams to differentiate between bone, fat mass, and lean mass by body region. The scan takes about 10 minutes and you lie still on a padded table.

Accuracy: ±1–2% body fat. DEXA also provides regional breakdowns (left arm, right leg, trunk, etc.) and bone mineral density, which makes it uniquely useful for tracking specific changes.

Note: DEXA scans tend to report body fat 3–5% higher than circumference methods like the Navy tape method. Do not compare a DEXA reading directly to a Navy method reading; use one or the other consistently.

Best for: People who want the most accurate reading available, athletes tracking specific body regions, or anyone concerned about bone density. Available at many hospitals, clinics, and specialty fitness centers.

5. Hydrostatic (Underwater) Weighing

Hydrostatic weighing was the gold standard before DEXA. It compares your weight on land to your weight fully submerged in water. Fat is less dense than muscle and bone, so the density difference reveals body fat percentage. You exhale as much air as possible and sit underwater on a special chair while being weighed.

Accuracy: ±1–2% body fat, similar to DEXA.

Best for: People with access to a research lab or university facility. Hydrostatic weighing is rarely available commercially anymore because DEXA is easier and equally accurate.

Bonus: Bod Pod (Air Displacement Plethysmography)

The Bod Pod is an egg-shaped chamber that measures body volume using air displacement instead of water. You sit inside for a few minutes while the device calculates your body density and converts it to body fat percentage. It is a dry, painless alternative to hydrostatic weighing.

Accuracy: ±2–3% body fat. Slightly less accurate than DEXA but more comfortable and faster than underwater weighing.

Cost: $50–$100 per scan, available at some fitness centers and universities.

How to Measure Body Fat Percentage at Home (Step by Step)

The U.S. Navy tape method is the best option for at-home measurement. It requires only a flexible measuring tape, takes about 3 minutes, and is accurate to within 1–3% body fat. Follow these steps for the most consistent results.

Which Method Is Right for You?

The right method depends on your goals, budget, and what you have access to:

• Most people: Start with the Navy tape method. It is free, takes 3 minutes, and accurate enough for tracking progress.
• Serious athletes or bodybuilders: Get one DEXA scan at the start, then use the Navy method or skinfolds for regular tracking.
• People who own a smart scale: Use it for trend tracking, but do not rely on individual readings. Pair with the Navy method for a reality check.
• People with access to a trainer: Skinfold calipers from a trained person are accurate and repeatable.
• People focused on bone density or regional fat: DEXA is the only method that gives you this information.

Frequently Asked Questions