Health & Fitness
Body Fat Calculator
Estimate body fat percentage from tape measurements, with fat mass, lean mass, and a goal weight.
Result
Enter your numbers and press Calculate to see the result.
Calculating…
How body fat is estimated from tape measurements
This calculator uses the US Navy circumference method, developed so body composition could be assessed with nothing but a tape measure. It compares girth at the waist and neck against height — the idea being that fat accumulates at the waist while the neck stays comparatively stable.
| Sex | Formula (metric, cm) |
|---|---|
| Men | 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450 |
| Women | 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450 |
Women's measurements include the hip because female fat distribution is more gluteofemoral, and a waist reading alone would systematically under-report it.
How to measure correctly
The method is only as good as the tape work, and measurement error is by far the largest source of a wrong result.
- Neck — just below the larynx, tape sloping slightly downward at the front. Do not flex.
- Waist — at the navel for men, at the narrowest point for women. Measure at the end of a normal exhale, without pulling the tape tight or holding your stomach in.
- Hip — the widest point of the buttocks, feet together.
Take each measurement three times and use the average. Measure at the same time of day, ideally in the morning before eating, because waist readings drift by a centimetre or more across a day.
Body fat percentage ranges
Healthy ranges differ substantially between men and women. Women carry more essential fat — the minimum needed for hormonal and reproductive function — which is a physiological difference, not a fitness one.
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | 25%+ | 32%+ |
Body fat by age
Body fat rises with age even at a stable weight, because muscle mass declines from roughly the fourth decade onward. A percentage that is unremarkable at 55 would be high at 25.
| Age | Healthy range, men | Healthy range, women |
|---|---|---|
| 20–39 | 8–19% | 21–32% |
| 40–59 | 11–21% | 23–33% |
| 60–79 | 13–24% | 24–35% |
These are population reference ranges rather than targets. They describe what is typical and healthy, not what is optimal for any individual.
What body fat percentage do you need for visible abs?
Abdominal definition appears at roughly 10–12% for men and 18–20% for women. Two caveats matter more than the number. Fat distribution is largely genetic, so two people at the same percentage can look very different. And the bottom of these ranges is difficult to hold year-round — physique athletes reach it for competition and come back up afterwards, which is normal rather than a failure.
Body fat and BMI answer different questions
BMI compares weight to height and knows nothing about what the weight is made of. A muscular athlete and a sedentary person of the same height and weight have identical BMI and completely different body composition — which is the entire reason body fat percentage is worth measuring.
The BMI-based cross-check shown in the results uses the Deurenberg equation, which estimates body fat from BMI, age, and sex. It is included for comparison only: it inherits BMI's blindness to muscle, so a large gap between the two figures usually means you carry more or less muscle than average.
How accurate is this?
The Navy method is typically within 3–4 percentage points of a DEXA scan, which is enough to track change over months but not enough to argue about a single decimal. Ranked roughly by accuracy:
| Method | Typical error | Practicality |
|---|---|---|
| DEXA scan | ±1–2% | Clinic visit, paid |
| Skinfold calipers (7-site) | ±3% | Cheap, needs a trained tester |
| Navy circumference method | ±3–4% | A tape measure |
| Bioelectrical impedance scales | ±4–8% | Instant, but swings with hydration |
Use one method consistently and watch the trend rather than the absolute figure. A scale that reads 3% low every time is still perfectly useful for telling you which direction you are heading.
This is a general estimate, not a medical assessment. For daily energy needs and macro targets, use the calorie and TDEE calculator; for resting metabolism, the BMR calculator can take a body fat figure and apply the Katch-McArdle equation.
Body Fat Calculator — frequently asked questions
How is body fat calculated from measurements?
This calculator uses the US Navy circumference method, which compares waist and neck girth against height. Women's measurements also include the hip, because a waist reading alone under-reports female fat distribution.
What is a healthy body fat percentage?
For men, roughly 14 to 24% covers fitness through average. For women it is 21 to 31%. Women carry more essential fat for hormonal function, so the ranges are not comparable between sexes.
What body fat percentage do you need for visible abs?
Around 10 to 12% for men and 18 to 20% for women. Distribution is largely genetic, so two people at the same percentage can look quite different, and the bottom of these ranges is hard to hold year-round.
How accurate is the Navy body fat method?
Typically within 3 to 4 percentage points of a DEXA scan. That is enough to track change over months, but not enough to treat a single decimal as meaningful. Measure consistently and watch the trend.
How is body fat different from BMI?
BMI compares weight to height and cannot tell muscle from fat. A muscular athlete and a sedentary person of the same height and weight have identical BMI and very different body composition.
Does body fat percentage change with age?
Yes. It rises with age even at a stable weight, because muscle mass declines from around the fourth decade. Healthy reference ranges shift up by several points between the 20s and the 60s.