Estimate your body fat percentage from a few tape measurements, and see what it means in kilograms.
Estimates are for general guidance only and are not medical advice. For a personalised plan, book a free guided tour at RPM Gym.
The percentage is an estimate from circumferences, not a measurement of your tissue. The US Navy equation infers fat from the relationship between girths and height, which works because fat distributes predictably enough across a population — and works less well the further you sit from that population.
The kilogram figures are usually more useful than the percentage. Lean mass is what training and protein are there to protect, and watching it hold while fat mass falls is a far better read on a diet than the percentage alone.
Where this differs from BMI is worth stating plainly: BMI can't distinguish muscle from fat at all, while this at least attempts to. Neither is a substitute for the other, and both are screening estimates rather than diagnoses.
| Essential fat | Men 2–5% · Women 10–13% | The minimum required for normal physiological function. Not a target. |
|---|---|---|
| Athletes | Men 6–13% · Women 14–20% | Typical of people training seriously in a sport with a body-composition component. |
| Fitness | Men 14–17% · Women 21–24% | Common among people who train consistently and aren't dieting. |
| Average | Men 18–24% · Women 25–31% | The range most adults fall in. It's a description of a population, not a verdict on an individual. |
| Above average | Men 25%+ · Women 32%+ | Worth discussing with a doctor alongside waist measurement and medical history rather than acting on alone. |
Men: %fat = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450 Women: %fat = 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.221 × log₁₀(height)) − 450 Lean mass = weight × (1 − %fat ÷ 100)
A man 180 cm tall, 82 kg, with a 39 cm neck and an 88 cm waist.
About 17.6% body fat: roughly 67.5 kg of lean mass carrying 14.5 kg of fat.
It sits within roughly 3–4 percentage points of laboratory methods for most people, which is reasonable for a tape measure and free. It's least accurate at the extremes — very lean, very heavy, or unusually muscular builds.
At the navel, standing relaxed, at the end of a normal exhale. Keep the tape level all the way round and snug without compressing the skin. Don't brace or pull your stomach in. That's the single most common way people get an implausibly low result.
The Navy equations differ by sex. The female version includes hip circumference because fat distribution patterns differ; the male version uses only neck, waist and height, so the hip field doesn't apply.
It depends on what you're training for, and the honest answer is that the bands above describe populations rather than prescribing targets. Athletes in weight-sensitive sports sit lower than people training for general health, and lower isn't automatically better — essential fat exists for a reason.
For understanding your own body composition, this is the more informative of the two, because BMI can't separate muscle from fat. BMI remains useful as a population screening tool. Neither replaces a waist measurement.
Almost always measurement variance rather than real change: tape placement, time of day, hydration and food in the gut all shift girths by a centimetre or more. Trust an eight-week trend measured consistently, not a single reading.
Which of those two numbers moves is a training and protein question. Book a free guided tour at RPM Gym in Al Manhal.