Quick Answer
The US Navy method estimates body fat from height and tape measurements. For men it uses neck and waist; for women neck, waist and hips. Example: a man 170 cm tall with a 38 cm neck and an 85 cm waist has about 17.8% body fat — in the Fitness range (14–17%) on the edge of Average. A woman 160 cm tall with a 33 cm neck, 75 cm waist and 97 cm hips comes out at about 29.3% (Average). Expect an error of a few percentage points.
What is a Body Fat Calculator?
A body fat calculator (बॉडी फैट कैलकुलेटर) estimates what percentage of your body weight is fat. Two people with the same height and weight can look and feel very different — one muscular, the other carrying more fat — and body fat percentage captures that difference far better than weight or BMI alone. It is a useful way to track progress when you are exercising, because the scale may barely move while you lose fat and gain muscle.
This free tool uses the US Navy circumference method, which needs only a soft tape measure. Enter your height and a few measurements and it shows your estimated body fat percentage, your category, your fat mass and lean mass, and a BMI-based estimate for comparison.
Key Features
- US Navy formula for men and women.
- ACE category — essential, athletes, fitness, average or obese.
- Fat mass and lean mass in kg or lb.
- BMI-based Deurenberg estimate for comparison.
- Metric or imperial measurements.
- Private: nothing leaves your browser.
How to Measure Correctly
Accuracy depends mostly on measuring well. Use a soft, non-stretch tape, stand relaxed and breathe out normally.
- Height: without shoes, back against a wall.
- Neck: just below the larynx (Adam's apple), with the tape sloping slightly downward at the front. Do not flare the neck.
- Waist — men: horizontally at the level of the navel.
- Waist — women: at the narrowest point, usually a little above the navel.
- Hips — women: at the widest part of the buttocks.
Keep the tape level and snug against the skin without pressing in. Take each measurement three times and use the average. Measure in the morning, before eating, for the most consistent results.
How to Use the Calculator
- Choose male or female and your units.
- Enter height, weight and age.
- Enter your neck and waist — and hips if female.
- Read your body fat %, category, fat mass and lean mass.
The US Navy Formulas
With all measurements in centimetres:
- Men: %BF = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
- Women: %BF = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
Example (man): height 170 cm, neck 38 cm, waist 85 cm → about 17.8%. At 75 kg that is about 13.3 kg of fat and 61.7 kg of lean mass.
Example (woman): height 160 cm, neck 33 cm, waist 75 cm, hips 97 cm → about 29.3%, in the average range.
The logic is simple: fat tends to collect around the waist (and hips in women), while the neck stays relatively lean. A bigger difference between waist and neck means more body fat for a given height.
Body Fat Categories (ACE)
| 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% and above | 32% and above |
These ranges come from the American Council on Exercise. Healthy body fat tends to rise a little with age, and very low body fat is not automatically healthier — essential fat supports hormones, organs and, for women, reproductive health.
Body Fat vs BMI
BMI divides weight by height squared. It is quick and useful for populations, but it cannot tell muscle from fat. A muscular athlete may be "overweight" by BMI with low body fat, while someone with a normal BMI can carry a high percentage of fat, especially around the waist. The calculator shows a Deurenberg estimate based on BMI, age and sex next to the tape result so you can see the difference. For the 170 cm, 75 kg man in our example, BMI is 26.0 and the BMI-based estimate is about 21.8%, while the tape method gives 17.8%. Check your BMI with our BMI Calculator.
How Accurate Is It — and Other Methods
| Method | Notes |
|---|---|
| US Navy tape (this tool) | Free and easy; usually within a few percentage points |
| Skinfold calipers | Good in trained hands; depends on the tester |
| Smart scales (BIA) | Convenient; affected by hydration and recent meals |
| DEXA scan | Very accurate reference method; costs money |
| Hydrostatic weighing / Bod Pod | Accurate; mostly in labs and sports centres |
No home method is perfect. What matters most is using the same method consistently and watching the trend over weeks and months.
Using Body Fat to Track Progress
When you start strength training, your weight may stay the same while your waist shrinks — a sign you are losing fat and gaining muscle. Body fat percentage captures that. Re-measure every two to four weeks. If you are cutting fat, aim for a gradual decline; losing more than about 1% of body weight a week often means losing muscle too. Our BMR Calculator uses your lean mass in the Katch-McArdle formula for a more personal calorie estimate.
Example: Twelve Weeks of Training
Our 170 cm example man starts a programme of three strength sessions a week, daily walks and a modest calorie deficit. Here is how his numbers could change:
| Week | Weight | Waist | Body fat | Fat mass | Lean mass |
|---|---|---|---|---|---|
| 0 | 75 kg | 85 cm | 17.8% | 13.3 kg | 61.7 kg |
| 6 | 74 kg | 82 cm | 15.4% | 11.4 kg | 62.6 kg |
| 12 | 73 kg | 80 cm | 13.7% | 10.0 kg | 63.0 kg |
The scale shows only a 2 kg drop, which might feel disappointing. But body fat fell from 17.8% to 13.7%: he lost about 3.3 kg of fat and gained about 1.3 kg of lean mass. That is exactly the kind of progress body fat percentage reveals and weight alone hides. (Neck size is assumed unchanged at 38 cm.)
Why Waist Size Matters
Fat stored around the abdomen (visceral fat) is linked with a higher risk of type 2 diabetes, heart disease and high blood pressure. Many health guidelines for Indian adults treat a waist above about 90 cm in men and 80 cm in women as a warning sign worth discussing with a doctor. Even without calculating body fat, tracking your waist is a simple and valuable health habit.
Who Should Interpret Results Carefully
The Navy formulas were developed on adult military personnel. They may be less accurate for very muscular strength athletes, people with a large waist due to bloating or pregnancy, older adults and people of very short or tall stature. If you are using body fat for a medical decision, ask your doctor about a clinical measurement.
Tips to Lower Body Fat
- Small calorie deficit — about 300–500 kcal below your daily needs.
- Strength training 2–3 times a week to keep muscle.
- Enough protein at every meal.
- Daily movement — walking counts.
- Sleep 7–9 hours and manage stress.
- Limit sugary drinks and ultra-processed snacks.
Common Mistakes
- Measuring the waist in the wrong place — men at the navel, women at the narrowest point.
- Pulling the tape too tight or holding the breath.
- Comparing different methods — a smart scale and the tape method will rarely agree exactly.
- Reacting to one reading instead of the trend.
Quick Glossary
- Body fat %: fat mass as a share of total weight.
- Fat mass: weight × body fat %.
- Lean mass: everything else — muscle, bone, organs, water.
- Visceral fat: fat stored around internal organs.
- DEXA: a low-dose X-ray scan that measures body composition.
Why Use This Body Fat Calculator?
It needs nothing more than a tape measure, explains exactly where to measure, works in centimetres or inches and gives you fat mass, lean mass and your category in one view. It is free, private and quick enough to repeat every few weeks as you track your progress. Write your readings in a notebook or spreadsheet, and you will have a clear record of how your body is changing.
Body Fat Calculator — Key Facts
| Method | US Navy circumference formula |
|---|---|
| Men measure | Height, neck, waist (at navel) |
| Women measure | Height, neck, waist (narrowest), hips |
| Average range | Men 18–24% · women 25–31% (ACE) |
| Example | Man 170 cm, neck 38, waist 85 → ≈ 17.8% |
| Accuracy | Usually within a few percentage points |
Frequently Asked Questions
How does the US Navy body fat method work?
It uses the fact that fat collects around the waist (and hips in women) while the neck stays relatively lean. Formulas developed for the US Navy combine height with these circumferences to estimate body fat percentage.
How accurate is the Navy method?
For most people it is usually within a few percentage points of lab methods such as DEXA. It is less accurate for very muscular people, those with an unusual fat distribution and older adults. Consistent measuring technique matters most.
Where exactly should I measure?
Neck: just below the larynx (Adam's apple), tape sloping slightly down to the front. Waist: men at the navel; women at the narrowest point. Hips (women): at the widest point of the buttocks. Keep the tape snug but not pressing into the skin.
What is a healthy body fat percentage?
The American Council on Exercise lists average ranges of 18–24% for men and 25–31% for women, fitness ranges of 14–17% and 21–24%, and obesity from 25% (men) and 32% (women). Healthy ranges also rise somewhat with age.
Why do women have higher body fat?
Women need more essential fat for hormonal and reproductive health. ACE lists essential fat as 10–13% for women and 2–5% for men.
Is body fat better than BMI?
It tells you more about body composition. BMI cannot tell muscle from fat, so a muscular person may have a high BMI with low body fat. Using both together gives a better picture.
What is lean body mass?
Everything that is not fat: muscle, bone, organs and water. Lean mass = weight × (1 − body fat %). It is used in the Katch-McArdle BMR formula and for protein targets.
What is the BMI-based estimate?
The Deurenberg formula estimates body fat from BMI, age and sex. It needs no tape, but because BMI ignores muscle it is a rougher guide; it is shown for comparison.
How often should I measure?
Every 2–4 weeks is enough. Measure at the same time of day — ideally in the morning before eating — and take each measurement three times.
Can I use inches?
Yes. Switch the units to ft-in / lb and enter your measurements in inches; the calculator converts them exactly.
Does it work for children?
No. These formulas are for adults. Children's body composition is assessed with age- and sex-specific growth charts by a doctor.
Is my data saved?
No. Everything is calculated in your browser and nothing is stored or sent.
Know Your Body Fat!
Free body fat calculator — just a tape measure needed.
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