How to Calculate Body Fat Percentage
Your weight tells you how heavy you are. Your body fat percentage tells you what that weight is made of — and that is the number that matters for health. Two people can weigh 80 kg, yet one carries 12 kg of fat and the other carries 25 kg, and their health risks are completely different. The body fat calculator above works out your percentage from a few tape measurements, using the US Navy method.
This page shows you the Navy formula, how to measure yourself correctly, two worked examples, and the charts that show where your number sits. It also explains what the result means, how accurate it is, and what to do with it once you know it.
How to measure: waist at the navel for men, at the narrowest point for women; neck just below the Adam’s apple with the tape sloping slightly down at the front; hips at the widest point. Keep the tape snug but not tight, and don’t hold your stomach in.
The Navy Method Formula
The US Navy method estimates body fat from circumference measurements — no scales, no calipers, no lab visit. It was developed by the US Navy to assess the fitness of sailors, and it is still used by the American military today. The formulas use logarithms, so they look intimidating, but the calculator does the maths for you.
Men: Body fat % = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
Women: Body fat % = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
All measurements are in centimetres. Men need three: height, neck and waist. Women need four: height, neck, waist and hip. The waist-minus-neck term is the heart of the method: the bigger your waist is relative to your neck, the more fat you carry.
How to Measure Yourself
A body fat result is only as good as the measurements behind it. Measure in the morning, standing relaxed, with a flexible tape held snug but not tight. Do not hold your stomach in and do not pull the tape so hard it dents the skin. Take each measurement twice and use the average.
- Neck: just below the Adam’s apple, with the tape sloping slightly down at the front.
- Waist (men): at the navel, with the tape level around the body.
- Waist (women): at the narrowest point, usually just above the navel.
- Hip (women): at the widest point around the buttocks.
- Height: barefoot, standing straight against a wall.
Worked Example: A Man at 16.9% Body Fat
Take a man who weighs 70 kg, is 175 cm tall, with a neck of 38 cm and a waist of 85 cm. The waist-minus-neck difference is 47 cm. Plugging the numbers into the Navy formula gives a body fat percentage of 16.9%. That puts him in the Fitness category — lean, healthy, and well inside the range linked with the lowest health risks. His fat mass is 70 × 16.9% = 11.9 kg, and his lean mass is 70 − 11.9 = 58.1 kg. The calculator above shows exactly this result with its default measurements, including the fat and lean breakdown.
| Measure | Value |
|---|---|
| Body weight | 70.0 kg |
| Body fat percentage | 16.9% |
| Fat mass | 11.9 kg |
| Lean body mass | 58.1 kg |
| Category | Fitness |
Worked Example: A Woman at 24.9% Body Fat
Now a woman who weighs 60 kg, is 165 cm tall, with a neck of 32 cm, a waist of 70 cm and hips of 95 cm. Her waist-plus-hip-minus-neck is 70 + 95 − 32 = 133 cm. The Navy formula gives 24.9% body fat, which is in the Fitness category for women. Her fat mass is 60 × 24.9% = 14.9 kg and her lean mass is 60 − 14.9 = 45.1 kg. Women carry more essential fat than men — about 10 to 13 percent against 2 to 5 percent for men — so the same percentage means something different for each sex, and the categories in the chart below reflect that.
Body Fat Percentage Chart
Read your result against the chart below. The bands come from the American Council on Exercise, and they are the standard reference used by trainers and health professionals.
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athlete | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25% and above | 32% and above |
Essential fat is the minimum your body needs to function — for hormones, insulation and protecting organs. Going below it is dangerous, especially for women, where it can stop menstruation and weaken bones. Athlete levels are seen in competitive sportspeople. Fitness is the band most active, healthy adults sit in. Average is where most of the population sits, and it is the band where health risks start to climb. Above 25% for men and 32% for women, the risk of type 2 diabetes, heart disease and high blood pressure rises substantially.
How Accurate Is the Navy Method?
The Navy method is typically accurate to within 3 to 4 percentage points of lab methods such as DEXA scans and hydrostatic weighing. That means a reading of 20% could really be anywhere from 16% to 24% — so treat it as a good estimate, not a precise measurement. Its strength is consistency: if you measure the same way every time, the trend over weeks and months is reliable even if the absolute number is a few points out. For the most accurate result, measure in the morning, use the same tape, and have someone else take the waist measurement if you can.
Other Ways to Measure Body Fat
- DEXA scan: the most accurate common method, within 1 to 2 points, but it needs a clinic visit and costs money.
- Hydrostatic weighing: very accurate, but you have to be weighed underwater in a tank.
- Skinfold calipers: cheap and quick, but accuracy depends entirely on the skill of the person measuring.
- Bioelectrical impedance scales: convenient, but readings swing by several points with hydration, food and time of day.
- Visual estimates: comparing yourself to photos is free and surprisingly useful for a rough band, but not for tracking small changes.
What to Do With Your Result
Your body fat percentage is most useful when combined with your weight and your calorie plan. If you are in the Average or Obese band and want to lose fat, find your daily target with the calorie calculator and aim for a 500-calorie deficit. Feed your lean mass into the BMR calculator with the Katch-McArdle formula for a more accurate resting burn. And check your BMI for the weight-category view — the two numbers together tell you far more than either alone.
- Measure yourself and get your percentage from the calculator above.
- Note your fat mass and lean mass, not just the percentage.
- Set a target band — Fitness is a good goal for most adults.
- Plan your calories with a 500 deficit if you need to lose fat.
- Train with weights twice a week to protect lean mass while you diet.
- Re-measure every four weeks, under the same conditions.
Losing Fat Without Losing Muscle
When you diet, your body loses both fat and muscle. The split depends on protein and training. Without strength training and with low protein, up to a quarter of the weight you lose can be muscle. With 1.6 to 2.0 g of protein per kg of body weight a day and two weight sessions a week, most of the loss is fat. That matters because muscle is what keeps your metabolism up — lose it and your daily calorie needs fall, making the fat harder to keep off. Track your lean mass in the calculator result, not just the percentage: if lean mass is falling, eat more protein and lift more.
Related tools: your resting burn from the BMR calculator, your daily target from the calorie calculator, and your target weight from the ideal weight calculator. The Centers for Disease Control and Prevention explains how body fat and BMI relate to health risk.
Quick Reference
Use the body fat calculator above with your own numbers, and keep the reference figures below handy while you plan.
| Person | Body fat | Fat mass | Lean mass | Category |
|---|---|---|---|---|
| Man, 70 kg, 175 cm | 16.9% | 11.9 kg | 58.1 kg | Fitness |
| Woman, 60 kg, 165 cm | 24.9% | 14.9 kg | 45.1 kg | Fitness |
| Man, 90 kg, 180 cm | 21.9% | 19.7 kg | 70.3 kg | Average |
What to remember
- Body fat percentage tells you what your weight is made of — weight alone cannot.
- The Navy method is accurate to within 3 to 4 percentage points of lab tests.
- Fitness is 14 to 17 percent for men and 21 to 24 percent for women.
- Women need more essential fat than men: 10 to 13 percent against 2 to 5 percent.
- Track fat mass and lean mass, not just the percentage, so you know what you are losing.
Your checklist
- Measure in the morning with a flexible tape, standing relaxed.
- Men: height, neck and waist. Women: add the hip measurement.
- Enter the numbers in the calculator above and note your percentage, fat mass and lean mass.
- Compare with the chart to find your category.
- Re-measure every four weeks, the same way, and track the trend.
Mistakes to avoid
- Holding your stomach in while measuring the waist — it flatters the result by 2 to 3 points.
- Measuring after a meal, when food and water add centimetres to the waist.
- Flexing your neck, which inflates the neck measurement.
- Expecting lab precision from a tape measure — the Navy method is an estimate.
- Chasing essential-fat levels, which are unhealthy to maintain.
Frequently Asked Questions
How do I calculate my body fat percentage at home?
Use the Navy method: measure your height, neck and waist (plus hips for women) with a tape, then enter them in the calculator above. For a man at 70 kg, 175 cm, neck 38 cm and waist 85 cm, the result is 16.9% body fat, with 11.9 kg of fat and 58.1 kg of lean mass.
What is a healthy body fat percentage?
For men, 14 to 17 percent is the Fitness band and 18 to 24 percent is Average. For women, 21 to 24 percent is Fitness and 25 to 31 percent is Average. Below 6 percent for men or 14 percent for women is approaching essential-fat levels and is not healthy to maintain.
How accurate is the Navy body fat method?
Typically within 3 to 4 percentage points of lab methods like DEXA. That makes it a good estimate rather than a precise measurement. Its real strength is tracking change over time: measure the same way every four weeks and the trend is reliable.
Why is my body fat percentage different from my BMI?
BMI uses only weight and height, so it cannot tell muscle from fat. A muscular person can have a high BMI and a low body fat percentage. Body fat percentage measures composition directly, which is why the two numbers disagree for athletes and lifters.
How often should I measure body fat?
Every four weeks, under the same conditions — morning, before eating, with the same tape. More often than that and you will mostly be measuring water and measurement error, not real change.
Can I reduce body fat without losing weight?
Yes — this is body recomposition. By eating at maintenance, training with weights and eating enough protein, you can lose fat and gain muscle at the same time, so the scale barely moves while your percentage falls. It works best for beginners and people returning to training.
Disclaimer: This calculator provides estimates for general information only and is not medical advice. The Navy method is accurate to within 3 to 4 percentage points and is not a substitute for clinical body composition testing. Consult a doctor before starting a fat-loss plan, especially if you have a medical condition.