The US Navy tape method
Developed for military body composition screening, this method estimates body fat from circumference measurements and height using a logarithmic regression. For men it uses waist and neck; for women it adds the hip measurement, because fat distribution differs. It needs nothing but a tape measure and takes a minute.
Measuring properly
- Neck: just below the larynx, tape sloping slightly down at the front.
- Waist: men measure at the navel; women at the narrowest point of the torso.
- Hip: the widest point around the buttocks.
Measure first thing in the morning, before eating, standing relaxed and breathing out normally. Do not pull the tape tight enough to compress the skin. Repeat each measurement three times and use the middle value — inconsistent technique causes more error than the formula does.
Typical ranges
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | 25%+ | 32%+ |
Why body fat matters more than body weight
The number on the scale cannot tell the difference between muscle and fat, which is why two people of the same height and weight can look and function completely differently. Body fat percentage measures what your weight is actually made of, and that composition is what drives health outcomes. Carrying too little is dangerous — the body needs essential fat to protect organs, absorb vitamins and regulate hormones — but carrying too much, particularly around the abdomen, is linked to heart disease, type 2 diabetes and other metabolic problems. This is why a lean, muscular person can weigh more than a chart says they should and still be perfectly healthy, while someone at a "normal" weight with little muscle can carry a risky amount of fat.
Where fat sits changes the risk
Two people with the same body fat percentage do not necessarily carry the same risk, because location matters. Fat stored around the abdomen and packed around the internal organs, called visceral fat, is far more strongly linked to disease than fat stored under the skin on the hips and thighs. This is part of why the tape method includes the waist measurement so prominently — a larger waist relative to your height is a warning sign in its own right, regardless of your overall percentage. A simple companion check is to keep your waist under half your height.
How to lower body fat
Reducing body fat comes down to a modest, sustained calorie deficit combined with enough protein and resistance training to protect muscle. The order matters: if you lose weight through diet alone, a meaningful share of the loss can come from muscle, which lowers the number on the scale but barely moves your body fat percentage. Keeping protein high and lifting weights tells the body to hold on to muscle and draw the deficit from fat instead. A deficit of roughly 300 to 500 calories a day is aggressive enough to show progress and gentle enough to sustain. To estimate the intake that creates that deficit, use the calorie calculator, and to see the resting energy those targets are built on, the BMR calculator.
How often should you measure?
Body fat changes slowly, so measuring daily only produces noise. Once every two to four weeks, taken under the same conditions — first thing in the morning, before eating, using the same tape and the same technique — gives a clean trend. Because the method's real value is in tracking change rather than in any single reading, consistency of technique matters more than precision on any one day. Write the numbers down and watch the direction over months, not days.
How the tape method compares to other tools
The most accurate methods — DEXA scans and hydrostatic weighing — are expensive and require a lab. Bioelectrical impedance scales, the kind that send a small current through your feet, are convenient but swing wildly with hydration, food and time of day, often by several percentage points between morning and evening. Skinfold calipers are accurate in trained hands but hard to use consistently on yourself. The tape method sits in a practical middle: free, repeatable at home, and consistent enough that the trend is trustworthy even if the absolute figure is approximate.
Accuracy and its limits
Against DEXA scanning, the Navy method typically lands within about three to four percentage points, and it is least reliable at the extremes — very lean and very heavy people both tend to be mis-estimated. Its real strength is consistency: measured the same way each month, the direction of change is meaningful even if the absolute number is approximate. Read it alongside your BMI, and see why body composition matters more than weight alone.