Body Fat Calculator
Estimate your body fat percentage from your height, neck, waist and hip measurements.
How to use the Body Fat Calculator
- Choose metric or US units and select your sex.
- Enter your age, weight and height.
- Measure your neck, waist and (for women) hips with a soft tape. Keep the tape level and snug but not tight.
- Press the Calculate button.
- Read your body fat percentage, fat mass, lean mass and category, and compare with the BMI-based estimate.
Body Fat Calculator: Estimate Your Body Fat Percentage
Quick answer: for adults aged 20 to 39, a healthy body fat range is roughly 21% to 32% for women and 8% to 19% for men. You can estimate yours at home with a tape measure and a body fat calculator.
Why Two People of the Same Weight Can Look Very Different
Your weight on the scale doesn’t say how much of you is fat and how much is muscle, bone and water. That is why two people with the same weight and height can have very different bodies. Body fat percentage is the share of your total weight that is fat, and it gives a clearer picture of your health than weight alone.
Types of Body Fat
- Essential fat is the minimum your body needs to live. It protects organs and supports nerves, hormones and reproduction. It is about 10% to 13% of body weight in women and 2% to 5% in men.
- Storage fat is the extra energy your body keeps. Some sits just under the skin (subcutaneous fat) and some inside the abdomen around the organs (visceral fat).
Everything that isn’t fat is lean mass: muscle, bone, water and organs.
Visceral fat matters most for health. It is linked to higher LDL (“bad”) cholesterol, lower HDL (“good”) cholesterol, insulin resistance, type 2 diabetes and heart disease. People of South Asian descent tend to carry more of it at the same BMI.
Why Body Fat Matters More Than BMI
BMI compares weight with height and cannot tell muscle from fat. A muscular person can have a high BMI with little body fat, while someone with low muscle can have a normal BMI and still carry too much fat. Body fat percentage also shows whether you are losing fat or just muscle and water when your weight changes.
How a Body Fat Calculator Works
A calculator can estimate your body fat using one or more of these methods.
1. The US Navy method (tape measure)
This method was developed at the Naval Health Research Center in the 1980s. It uses your height and a few body circumferences. The metric versions are:
All measurements are in centimetres. The result is an estimate that is often within a few percentage points of lab methods, but small measuring errors can change it noticeably.
2. The BMI method
This method estimates body fat from your BMI, age and sex. For adults:
It only needs height and weight, so it is easy, but it is the least accurate because it ignores muscle. Separate formulas exist for children, which is why adult calculators should not be used for anyone under 18.
3. Relative Fat Mass (RFM)
Some calculators also use RFM, which needs only height and waist: 64 − 20 × (height ÷ waist) for men and 76 − 20 × (height ÷ waist) for women.
Body Fat Calculator Examples
Example 1: a man
A 30-year-old man weighs 82 kg, is 178 cm tall and has a 92 cm waist and a 38 cm neck. His BMI is 25.9.
| Step | Result |
|---|---|
| US Navy method | 21.5% |
| BMI method | 21.8% |
| Fat mass (82 kg × 21.5%) | 17.6 kg |
| Lean mass (82 − 17.6) | 64.4 kg |
| Weight at 15% body fat (64.4 ÷ 0.85) | About 75.8 kg |
| Fat to lose to reach 15% | About 6.2 kg |
Example 2: a woman
A 32-year-old woman weighs 68 kg, is 165 cm tall and has a 78 cm waist, a 98 cm hip and a 32 cm neck. Her BMI is 25.0.
| Step | Result |
|---|---|
| US Navy method | 30.4% |
| BMI method | 31.9% |
| Fat mass (68 kg × 30.4%) | 20.7 kg |
| Lean mass (68 − 20.7) | 47.3 kg |
The two methods differ by a point or two, which is normal. A gap of more than about 8 points usually means a measurement needs rechecking.
What Is a Healthy Body Fat Percentage?
By age
| Age | Women | Men |
|---|---|---|
| 20 to 39 | 21% to 32% | 8% to 19% |
| 40 to 59 | 23% to 33% | 11% to 21% |
| 60 to 79 | 24% to 35% | 13% to 24% |
These ranges are drawn from a widely cited study of healthy adults and fit best people with a normal BMI. Women carry more fat than men because of hormones and reproduction.
Fitness categories (American Council on Exercise)
| Category | Women | Men |
|---|---|---|
| Essential fat | 10% to 13% | 2% to 5% |
| Athletes | 14% to 20% | 6% to 13% |
| Fitness | 21% to 24% | 14% to 17% |
| Average | 25% to 31% | 18% to 24% |
| Obese | 32% and above | 25% and above |
Jackson and Pollock ideal body fat
| Age | Women | Men |
|---|---|---|
| 20 | 17.7% | 8.5% |
| 30 | 19.3% | 12.7% |
| 40 | 22.2% | 15.3% |
| 50 | 25.2% | 18.9% |
All these tables are guides, not diagnoses. Athletes often sit lower, and older adults tend to sit a little higher. Having too little body fat is a health risk too. Staying at or below the essential range is something to discuss with a doctor.
How to Take Your Measurements
- Waist (men): measure around the level of the navel, standing relaxed and without pulling your stomach in.
- Waist (women): measure at the narrowest point of the waist.
- Neck: measure just below the larynx (Adam’s apple), with the tape sloping slightly down at the front. Don’t flare your neck.
- Hips (women): measure around the widest part of the hips and buttocks.
- Height: stand straight without shoes.
Measure to the nearest 0.5 cm, repeat each measurement twice and use the average. Use a soft tape that is snug but not squeezing, and measure at the same time of day, ideally in the morning. Small errors change the result, so be consistent.
Body Fat Measurement Methods Compared
| Method | Accuracy | Cost and access |
|---|---|---|
| DEXA scan | Very high (reference standard) | Clinic, paid |
| Hydrostatic weighing or BodPod | High | Specialist labs |
| Skinfold calipers (trained person) | Good | Gyms and trainers |
| US Navy tape method | Moderate | Free, at home |
| Relative Fat Mass | Moderate | Free, at home |
| Smart scales (bioimpedance) | Varies; affected by water | Cheap, at home |
| BMI-based formulas | Low | Free |
For home tracking, the best method is the one you can repeat under the same conditions every time.
Health Risks of Too Much or Too Little Body Fat
Excess body fat
Too much body fat, especially around the abdomen, is linked to type 2 diabetes, heart disease, stroke, sleep apnoea, fatty liver and some cancers. It can also affect hormones and fertility. Fat also behaves like an organ, releasing hormones and inflammatory proteins that can raise heart disease risk when levels are high.
Too little body fat
Very low body fat can disturb hormones, stop periods, reduce fertility, weaken bones and drain energy. Women need a minimum amount of fat to ovulate regularly, so extreme leanness is not a goal to chase.
Waist size and South Asian adults
Many guidelines suggest that South Asian adults face higher metabolic risk at smaller waist sizes. A commonly used warning level is a waist of about 90 cm or more for men and 80 cm or more for women. Ask your doctor which cut-offs apply to you.
Body Fat, Pregnancy and Trying to Conceive
Body fat calculators are not designed for pregnancy. Your body changes shape, your waist and hips grow and your weight rises to support the baby, so the formulas give misleading results. During pregnancy, follow your doctor’s guidance on healthy weight gain and use our pregnancy calculator to follow your weeks.
If you are planning a pregnancy, your weight and body fat before conception can affect ovulation and how your pregnancy goes. Checking your BMI and talking to your doctor is a good first step. Avoid crash diets, and do not try to lose weight while pregnant unless your doctor advises it.
How to Lower Body Fat Safely
- Make a modest calorie change. A small, steady deficit works better than an extreme diet.
- Eat enough protein to help protect your muscle while you lose fat.
- Lift weights or do strength work two to three times a week. More muscle keeps body fat percentage lower at the same weight.
- Walk every day. Raising your step count is an easy way to burn more calories.
- Sleep seven to nine hours and manage stress. Both affect appetite and belly fat.
- Be patient. Many people lose roughly half to one percentage point of body fat per month.
If you are pregnant, breastfeeding or have had an eating disorder, speak to a doctor before trying to change your body fat.
How Often Should You Measure?
Every two to four weeks is enough. Body fat changes slowly, and daily readings mostly reflect water, salt and measuring noise. Take photos or write down your waist measurement alongside the percentage to see the trend.
Common Mistakes
- Measuring the waist at the wrong spot, such as the hip bones, instead of at the navel or the narrowest point.
- Pulling the tape too tight or letting it sag.
- Comparing readings taken with different devices or at different times of day.
- Relying only on the BMI-based result, especially if you exercise regularly.
- Chasing a very low body fat percentage.
Body Fat Calculator FAQs
How do I calculate my body fat percentage?
Use a tape measure with the US Navy method, or use your height, weight, age and sex with a BMI-based formula. A calculator can do both for you in seconds.
What is a good body fat percentage?
For adults aged 20 to 39, roughly 21% to 32% for women and 8% to 19% for men. The healthy range rises a little with age.
Is the US Navy method accurate?
It is a useful home estimate and is often within a few percentage points of lab methods, but it is not perfect and depends on careful measuring.
Which is better, BMI or body fat percentage?
Body fat percentage describes your body composition better, because BMI cannot tell fat from muscle.
Can I calculate body fat with only my height and weight?
Yes, using the BMI method, but it is the least accurate. Adding your waist and neck measurements gives a much better estimate.
Why do different methods give different results?
Each method uses different inputs and assumptions. A difference of a few points is normal. If the results are more than about 8 points apart, measure again.
Is 10% body fat healthy?
For men it falls in the athletic range and can be healthy for some people. For women 10% is at the very bottom of the essential fat range and is usually too low to maintain.
Does muscle weigh more than fat?
No. A kilogram of muscle weighs the same as a kilogram of fat, but muscle takes up less space.
Can I use a body fat calculator during pregnancy?
No. Pregnancy changes your measurements and weight, so the results won’t be reliable. Follow your doctor’s advice instead.
Final Thoughts
Body fat percentage gives you a clearer view of your health and progress than your weight alone. Measure carefully, compare more than one method, watch the trend over weeks and combine it with a sensible eating plan, regular activity and strength training. If your result worries you, speak to a doctor.
Medical disclaimer: This article is for general information and education only. It is not a medical diagnosis or advice. Body fat calculators give estimates and may not be accurate for every person.
Please speak to a doctor if you have a health condition, are pregnant or breastfeeding, are under 18 or have had an eating disorder, before changing your diet or exercise routine.