Singapore
Singapore Body fat calculator
Your weight on the scale mixes muscle, bone, water and fat into one number, so two people of the same weight can carry very different amounts of fat. This calculator separates them. It uses the US Navy tape method, which reads body fat from a few circumference measurements you can take at home with a soft tape, and it shows a second estimate worked out from your BMI as a cross-check. Enter your sex, age, height and weight, then add your neck and waist measurements, plus your hip if you are a woman. The result is your estimated body fat as a percentage, the weight category it falls in, and a split of your weight into fat mass and lean mass. None of this needs a clinic visit or a special scale, and the tape method tracks change over weeks better than the scale alone, because it reacts to fat loss even when the scale stalls.
The US Navy tape method estimates body fat from circumference measurements and reads within a few points of a clinical scan for most people. The BMI estimate is a rougher cross-check. Neither replaces a DEXA or hydrostatic test. Measure relaxed, on bare skin, with the tape level and snug but not tight.
How it works
- Pick your sex; the Navy formula uses different constants and an extra hip measurement for women.
- Enter your height and weight, which feed the BMI cross-check, and your age, which the BMI estimate adjusts for.
- Measure your neck just below the larynx and your waist at the navel, keeping the tape level and snug but not pressing in.
- Women add the hip measurement at its widest point; the tool combines waist plus hip minus neck for them.
- The headline figure is the Navy estimate; the BMI-based number sits beside it, and the tool splits your weight into fat and lean mass.
Men: %fat = 495 / (1.0324 - 0.19077 x log10(waist - neck) + 0.15456 x log10(height)) - 450. Women add the hip: use log10(waist + hip - neck) with the female constants.
The Navy method takes the logarithm of the difference between your waist and neck, which stands in for the fat carried around the midsection, and scales it against your height. Women include the hip because their fat sits lower. The constants come from comparing tape measurements against underwater weighing in thousands of service members. The BMI cross-check uses a separate equation that needs only height, weight, age and sex.
- waist
- waist circumference in centimetres
- neck
- neck circumference in centimetres
- hip
- hip circumference in centimetres, women only
- height
- standing height in centimetres
Body fat categories (American Council on Exercise)
| Essential fat | Men 2 to 5%, women 10 to 13% | the minimum the body needs to function |
| Athletes | Men 6 to 13%, women 14 to 20% | typical of competitive sport |
| Fitness | Men 14 to 17%, women 21 to 24% | lean and active |
| Average | Men 18 to 24%, women 25 to 31% | common in the general population |
| Above average | Men 25%+, women 32%+ | higher health risk |
Worked example
A 30-year-old man, 178 cm and 80 kg, with a 38 cm neck and a 90 cm waist: The US Navy method returns about 20.2 percent body fat, which lands in the average band for men. That is roughly 16 kg of fat and 64 kg of lean mass. The BMI cross-check reads close, near 21 percent, so the two methods agree that this is a healthy but not athletic level.
Key facts
- A pound of fat and a pound of muscle weigh the same, but muscle takes up far less room, which is why body fat tells you more than weight alone.
- Women naturally carry more essential fat than men, so the healthy ranges are set higher for them.
- The Navy method needs only a tape measure and three measurements, no scale beyond your weight.
- Body fat above roughly 25 percent for men or 32 percent for women is linked to higher risk of metabolic disease.
Tips
- Take each measurement twice and use the average; a centimetre at the waist moves the result by about a point.
- Measure first thing in the morning before eating or drinking, so a meal or a salty dinner does not skew the tape.
- Track the trend over a month rather than reacting to one reading, since fat moves slowly.
- Pair this with the BMI and ideal weight tools to see your numbers from more than one angle.
Frequently asked questions
How accurate is the tape method?+
For most people the US Navy method reads within about 3 percentage points of a clinical scan, which is good enough to track progress month to month. It can drift for very lean or very heavy bodies, where a scan or a skinfold test is more reliable.
Where exactly do I measure?+
Neck goes just below the voice box, sloping slightly down at the front. Waist for men is at the navel, for women at the narrowest point. Hip is the widest part of the buttocks. Keep the tape horizontal and breathe normally rather than sucking in.
Why does the calculator ask for my hip only sometimes?+
The Navy equation for women includes the hip because fat distribution differs by sex; the equation for men does not use it. If you select male, the hip field is ignored.
What is a healthy body fat percentage?+
For men, fitness ranges run about 14 to 17 percent and average 18 to 24 percent; for women the same bands sit roughly 7 to 10 points higher because women carry more essential fat. Below the essential floor is unhealthy for either sex.
Why is the BMI estimate different from the tape one?+
BMI knows nothing about where your weight sits, so the Deurenberg estimate built on it can overstate fat for muscular people and understate it for those with little muscle. The two numbers agreeing is a sign your build is close to average; a wide gap usually means you are more or less muscular than typical.
How often should I remeasure?+
Every two to four weeks is enough. Fat changes slowly, and daily swings are mostly water. Measure at the same time of day, ideally in the morning, for a fair comparison.
Things to watch
- This is general guidance, not medical advice; a doctor or a DEXA scan gives a clinical figure.
- The tape method was built for healthy adults and is less reliable for athletes, very heavy bodies, pregnancy or children.
- Chasing a very low body fat percentage can harm health, especially for women, where it can disrupt hormones and periods.
Sources
- Prediction of percent body fat for US Navy men and women from body circumferences and height (Hodgdon & Beckett, 1984) · Naval Health Research Center
- Body mass index as a measure of body fatness: age- and sex-specific prediction formulas (Deurenberg et al., 1991) · British Journal of Nutrition
- Percent body fat norms · American Council on Exercise
Last updated: 2026
This is an estimate for general guidance, not financial, tax, legal or medical advice. Figures can change and individual circumstances vary. Always confirm with the official sources listed before making decisions.
Reviewed by Vikas Dulgunde.