Body Fat Calculator

This calculator estimates body fat percentage using the Circumference Method (US Navy formula) — one of the most accessible and reasonably accurate field methods, requiring nothing more than a flexible measuring tape. You enter your height and a few body measurements, and it returns an estimated body fat percentage along with a category band (essential fat, athletes, fitness, acceptable, or obese) so you can see roughly where you stand.

Treat this as a screening and tracking tool, not a clinical diagnosis. The circumference method estimates body composition from the relationship between girth measurements and average fat distribution across a population. It is excellent for spotting trends — watching the number fall as your waist shrinks over a few months — but it is not a substitute for a medical assessment or a lab-grade body-composition scan. If your result is in the obese range or you have health concerns, treat it as a prompt to consult a doctor or a qualified dietitian rather than a verdict.

Who this is for

It suits anyone on a fitness journey who wants a free, repeatable way to track fat loss without a gym caliper test or an expensive scan — people losing weight, recomposing, or simply curious how their measurements translate into a body-fat figure. Because it relies on a tape rather than a scale, it captures changes that weight alone hides: someone gaining muscle while losing fat may see a steady scale weight but a clearly falling body fat percentage here.

Circumference Formula

The tool uses the published US Navy equations, which are calibrated in inches (it converts your centimetre inputs internally):

Men: BF% = 495 / (1.0324 − 0.19077×log(waist−neck) + 0.15456×log(height)) − 450

Women: BF% = 495 / (1.29579 − 0.35004×log(waist+hip−neck) + 0.22100×log(height)) − 450

Men need height, neck and waist; women also need the hip measurement, because female fat distribution makes the hip girth an important input. The result area shows the exact equation it evaluated with your numbers, so the working is transparent.

Asia-Pacific context

The category bands shown here follow the widely used US/Western reference ranges. It is worth knowing that South Asian and other Asia-Pacific populations tend to carry more body fat — and more visceral fat around the abdomen — at a given BMI than Western populations, which is why bodies such as the WHO have suggested lower BMI action points for Asian groups. In practice that means an Indian user sitting at the upper end of the "acceptable" band may still benefit from trimming waist fat, and waist circumference itself is a useful companion metric. Use the trend in your own numbers over time as the primary guide rather than fixating on which side of a band boundary you fall.

Measurement tips

Neck: measure just below the larynx. Waist: measure at the navel (men) or the narrowest point (women). Hip (women): measure at the widest point. Stand straight, breathe normally, and don't suck in. Keep the tape snug but not tight, level all the way round, and measure on bare skin or a thin layer for consistency. For reliable tracking, measure at the same time of day — first thing in the morning before eating is ideal — and take each reading twice, using the average.

Worked example

A man who is 178 cm tall with a 38 cm neck and an 86 cm waist enters those three figures, and the calculator converts them to inches, evaluates the male equation, and returns an estimated body fat percentage in the fitness-to-acceptable region. Switching the sex toggle to female adds a hip field, because the female equation needs it. The companion Goal Mode then works the other way: give it your current weight and current body fat percentage and a target percentage, and it holds your lean mass constant to estimate the goal weight and how much fat you would need to lose to reach it.

Common mistakes to avoid

The most common errors are pulling the tape too tight, measuring over thick clothing, holding your breath or bracing your stomach, and measuring the waist at the wrong landmark. Any of these can shift the estimate by several percent. Remember the method carries a margin of error of roughly ±3–4%, so a single reading is best read as a range, not an exact figure — its real value is in the trend you build by measuring the same way each time.