Body fat percentage tells you something the scale can't: how much of your weight is fat versus muscle, bone, and water. Two people who weigh exactly the same can look completely different depending on their body composition. Here are the three most common ways to measure body fat, how they compare on accuracy and cost, and why a simple tape measure is good enough for most people.
What is body fat percentage?
Your body fat percentage is the share of your total weight made up of fat. The rest is your lean mass — muscle, organs, bone, and water. Some fat is essential: it protects organs and supports hormones, so healthy ranges never approach zero, and they're higher for women than men. Tracking body fat is often more useful than tracking weight alone, because it tells losing fat apart from losing muscle.
Method 1: The U.S. Navy tape method
The Navy method estimates body fat from a few body circumferences — neck and waist for men, plus hips for women — combined with your height. You measure with a flexible tape and a formula does the rest.
Pros and cons
- Pros: free, fast, no special equipment, and very repeatable if you measure the same way each time.
- Cons: it estimates from body shape rather than measuring fat directly, so it's less precise for very lean, very muscular, or very heavy bodies.
For tracking change over weeks and months, repeatability matters more than absolute precision — which is exactly what this method offers. Try it in the Body Fat Calculator.
Method 2: Skinfold calipers
Calipers pinch and measure the thickness of skinfolds at several body sites (commonly three or seven). The readings feed an equation that estimates total body fat. Done by a trained tester, calipers are quite accurate — often within three to four percentage points of a lab measurement.
- Pros: inexpensive, more direct than tape measurements, and well-validated.
- Cons: results depend heavily on the tester's skill and consistency, and self-testing is error-prone — especially reaching your own back and triceps.
Method 3: DEXA scan (the gold standard)
A DEXA (dual-energy X-ray absorptiometry) scan uses low-dose X-rays to measure fat, lean mass, and bone density, and even shows where fat sits on your body. It's the most accurate method widely available to the public.
- Pros: highly accurate and detailed, including a regional breakdown and bone density.
- Cons: costs money per scan, needs a clinic or lab, and involves a tiny radiation dose; readings can vary slightly between machines.
How the three methods compare
| Method | Accuracy | Cost | Convenience |
|---|---|---|---|
| U.S. Navy tape | Good (estimate) | Free | Very high — do it at home |
| Skinfold calipers | Very good (skilled tester) | Low | Medium — needs a tester |
| DEXA scan | Excellent (gold standard) | High per scan | Low — clinic visit |
Why the Navy method is good enough for most people
Unless you're a competitive athlete or have a clinical reason for a precise figure, the Navy method gives you what you actually need: a reasonable estimate and, more importantly, a consistent way to track progress. The trend over time — is your body fat falling while your weight holds, meaning you're keeping muscle? — matters far more than whether today's reading is 18.0% or 19.5%. Because it's free and repeatable, you can measure every couple of weeks and watch the direction of travel.
To measure well, use a snug (not tight) tape, take readings first thing in the morning, and measure the same spots each time: the neck just below the larynx, the waist at the navel for men or the narrowest point for women, and the hips at their widest point for women.
Body fat percentage vs BMI
BMI is a quick height-to-weight screen, but it can't tell fat from muscle — a muscular person can register as “overweight” on BMI while carrying low body fat. Body fat percentage answers the composition question directly, which is why it's the better fitness metric. Many people track both: use the BMI Calculator for a fast check and the Body Fat Calculator for composition.