You don’t need a lab or expensive scanner to estimate your body fat — a simple tape measure and the right formula get you surprisingly close. This guide shows you how to calculate body fat percentage at home using the U.S. Navy circumference method: where to place the tape, the exact formulas for men and women, a full worked example, and how to read your result against established healthy ranges. Body fat percentage tells you what the bathroom scale can’t — how much of your weight is fat versus muscle, bone, and water. To skip the logarithms, the free CalcRange Body Fat Calculator runs the same method from your measurements instantly.
What Is Body Fat Percentage?
Body fat percentage is the share of your total body weight that is fat tissue. An 80 kg person at 20% body fat carries 16 kg of fat and 64 kg of lean mass — muscle, bone, organs, and water.
It’s a more meaningful health and fitness measure than weight alone, because two people with identical weight and height can have completely different compositions. It also explains the classic dieter’s frustration: the scale can stall while body fat falls, if muscle is being gained at the same time.
Ways to Measure Body Fat
- DEXA scan: the clinical gold standard; accurate but costly and clinic-only.
- Skinfold calipers: good in trained hands; technique-sensitive.
- Bioelectrical impedance (smart scales): convenient but swings with hydration.
- Navy circumference method: tape measure + formula; studies place it typically within about 3–4 percentage points of DEXA — remarkable for a method costing nothing.
For tracking progress at home, the Navy method’s consistency matters more than its absolute accuracy: measure the same way each time and the trend is trustworthy.
How to Take Your Measurements
Use a flexible, non-stretch tape. Measure directly on skin, snug but not compressing, and take each measurement twice, averaging the results.
- Neck: just below the larynx (Adam’s apple), tape sloping slightly downward to the front.
- Waist — men: horizontally at navel level, relaxed, after a normal exhale.
- Waist — women: at the narrowest point of the torso.
- Hips — women only: at the widest point of the buttocks, feet together.
- Height: barefoot, against a wall.
The Navy Method Formula
All measurements in centimetres; log is the base-10 logarithm:
Men: Body fat % = 495 ÷ (1.0324 − 0.19077 × log(waist − neck) + 0.15456 × log(height)) − 450
Women: Body fat % = 495 ÷ (1.29579 − 0.35004 × log(waist + hip − neck) + 0.22100 × log(height)) − 450
The formulas estimate body density from the circumference differences — essentially how much of your torso is fat-storing girth versus frame — then convert density to a fat percentage. Nobody expects you to do logarithms on paper: this is precisely what the body fat calculator automates.
How to Calculate Body Fat Step by Step
- Measure neck, waist (and hips for women), and height as described above, in centimetres.
- Men: subtract neck from waist. Women: add waist and hips, subtract neck.
- Apply the formula — or enter the numbers into the calculator.
- Record the result with the date and conditions (morning, before eating is ideal).
- Repeat every 2–4 weeks under identical conditions to see the trend.
Worked Example
Profile: Man, 175 cm tall, waist 90 cm, neck 38 cm.
- Waist − neck = 52 cm
- log(52) = 1.716 → × 0.19077 = 0.327
- log(175) = 2.243 → × 0.15456 = 0.347
- Denominator = 1.0324 − 0.327 + 0.347 = 1.052
- Body fat = 495 ÷ 1.052 − 450 = ≈ 20.5%
In plain English: about a fifth of this man’s weight is fat — the upper end of the “average” band and within a healthy range for most adults his age. If he weighs 80 kg, that’s roughly 16.4 kg of fat mass and 63.6 kg of lean mass.
Calculate It Instantly
Take your three tape measurements, then let the CalcRange Body Fat Calculator handle the formula — it returns your percentage, fat mass, and lean mass in one go.
Healthy Body Fat Ranges
Widely used categories based on the American Council on Exercise (ACE) classification:
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Women naturally carry more fat than men — it’s biology, not a fitness gap. “Essential fat” is the minimum needed for hormones, organs, and health; going below it is dangerous, not impressive. Where fat sits also matters: abdominal fat carries more health risk, which is why the waist-to-hip ratio calculator is a useful companion measure.
What Changes Your Body Fat Percentage
- Energy balance. A sustained calorie deficit lowers fat mass; a surplus raises it. Set your target with the calorie calculator.
- Resistance training. Building muscle lowers the percentage even at constant fat mass — the denominator grows.
- Protein intake. Adequate protein protects muscle while dieting, steering weight loss toward fat.
- Age and hormones. Fat tends to rise and shift toward the abdomen with age; menopause accelerates the shift for women.
- Sleep and stress. Both influence appetite hormones and where fat is stored.
Common Measurement Mistakes
- Pulling the tape tight. Compressing the skin shrinks measurements and flatters the result — snug, not tight.
- Measuring at different times. Waist size changes after meals and through the day; always measure in the same conditions.
- Comparing across methods. Navy, calipers, and smart scales disagree systematically. Pick one method and track its trend.
- Reacting to single readings. Hydration alone moves estimates; judge 3-reading trends, not one-off numbers.
- Chasing athlete numbers. Very low body fat is a sport-specific, usually temporary state — not a general health target.
Frequently Asked Questions
What is a healthy body fat percentage?
For most adults, roughly 14–24% for men and 21–31% for women covers the fitness-to-average bands associated with good health. Ranges shift slightly upward with age, and athletes commonly sit below them during season.
How accurate is the Navy method?
Typically within 3–4 percentage points of a DEXA scan when measurements are taken carefully. Its real strength is repeatability: measured consistently, it tracks changes in your body fat reliably over time.
Can BMI tell me my body fat percentage?
No — BMI uses only height and weight, so it can’t separate muscle from fat. A muscular athlete and a sedentary person can share a BMI with very different body fat levels. Use BMI for population-level screening and body fat for composition.
How often should I measure body fat?
Every two to four weeks is plenty. Fat loss is slow — around 0.5–1% of body weight per week at best — so weekly tape sessions mostly measure noise.
How fast can I realistically lose body fat?
With a moderate calorie deficit and adequate protein, dropping about 0.5–1 percentage point of body fat per month is a strong, sustainable pace. Faster approaches tend to cost muscle, which defeats the purpose.
Why is my smart scale’s number so different?
Bioelectrical impedance estimates fat from how easily a current passes through you, which changes with hydration, food, and even foot calluses. Different method, different assumptions, different number — track one method’s trend rather than reconciling them.
Do I need to lose weight to lower my body fat percentage?
Not necessarily. Gaining muscle while holding weight steady lowers the percentage, since fat becomes a smaller share of the total. This “recomposition” is most achievable for beginners and returning trainees.
Conclusion
Calculating body fat percentage at home takes a tape measure, three careful measurements, and the Navy formula — or thirty seconds with a calculator. Read your result against the ACE ranges, remember that women’s healthy levels sit naturally higher, and judge progress by monthly trends measured under identical conditions. Start with today’s baseline using the free body fat calculator on CalcRange, and pair it with the BMI calculator and ideal weight calculator for a fuller picture of your starting point.
Sources and Further Reading
- Hodgdon JA, Beckett MB. “Prediction of percent body fat for U.S. Navy men and women from body circumferences and height.” Naval Health Research Center, 1984.
- American Council on Exercise (ACE) — body fat percentage categories.
- U.S. CDC — resources on body composition and healthy weight.
Further reading
For authoritative background on this topic, see Body fat percentage on Wikipedia.
Health disclaimer: This article and calculator provide general educational estimates and are not a substitute for professional medical advice, diagnosis, or treatment. For concerns about weight or body composition, consult a qualified healthcare professional.
Last reviewed: July 2026. Recommended editorial review: every 12 months.