Body fat percentage
A tape measure and three measurements give a body fat estimate that says considerably more than BMI, because this one does know what your weight is made of.
Your figures
Result
- Range
- Acceptable
- Fat mass (kg)
- 15.4
- Lean mass (kg)
- 64.6
The ranges for your sex
| Range | From |
|---|---|
| Essential fat | 0% |
| Athlete range | 6% |
| Fitness range | 14% |
| Acceptable | 18% |
| Above the acceptable range | 25% |
What we assume
- Uses the US Navy method (Hodgdon and Beckett, 1984).
- The category ranges are those of the American Council on Exercise.
- Hip circumference only enters the female formula.
- This is a circumference estimate: typical error is around 3-4 points.
How it is calculated
The method rests on a simple idea: the neck is almost all lean tissue and the waist is where fat gathers, so the difference between them tracks how much fat sits in between rather well. Height comes in to scale the result.
For men:
body fat % = 495 / (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
For women the hips are added, because fat distributes differently:
body fat % = 495 / (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.221 × log₁₀(height)) − 450
The ranges
For men: up to 5% is essential fat, 6 to 13 is the athlete range, 14 to 17 counts as fit, 18 to 24 acceptable, and 25 upwards is high. For women every band sits about 8-10 points higher, because female essential fat is higher for physiological reasons, not habits.
How much to trust it
Against a DEXA scan, which is the reference, this method is typically 3 or 4 points out, and it tends to underestimate on very lean people and overestimate on very muscular ones. It will not tell you your exact body fat.
What it is good for is tracking a change: measure the same way, at the same time of day, with the same tape, and the error repeats itself, so the difference between two readings is real even when the absolute number is not quite.
How to measure
A flexible tape, resting on skin without pulling tight or leaving slack, in the morning before eating. One extra centimetre at the waist moves the result by nearly a full point, so take each measurement twice and keep the one that repeats.
An example
A man of 1.75 m and 80 kg, with a 38 cm neck and an 88 cm waist, comes out at 19.2% body fat: the acceptable range. That is 15.4 kg of fat mass and 64.6 kg of lean mass.
Frequently asked questions
Is it more reliable than a bioimpedance scale?
They are comparable, and neither is exact. Bioimpedance depends heavily on hydration - the same person can read two points apart between morning and evening - while the tape depends on where you put your hands. Measure under consistent conditions and both are useful for trends.
Why does the female formula need hip measurement?
Because fat distributes differently. In women a significant share sits on hips and thighs, and without that measurement the formula would systematically underestimate.
I am male. Can I leave the hip field blank?
You can put any value in it: the male formula ignores it entirely. We keep it visible so the form does not have to change when you switch sex.
What percentage should I be at?
It depends a lot on age and on what you are training for. The fit and acceptable bands in the table cover most healthy people. Dropping below the essential fat range is not an athletic goal, it is a risk.
Keep calculating
All tools →- Body mass index calculator BMI is a one-line number that gets used constantly and understood rarely. Here it comes with the weight range for your height, and with the part the formula misses.
- Ideal weight for your height There is no ideal weight, there are four formulas that give four different numbers. Here they are together, with the BMI range alongside, so the real spread is visible.
- Daily calories you need How many calories you burn a day given your body and your activity, and the figure that matches each goal. Using the real 7,700 kcal per kilo, not the rounded "500 a day".
Updated on 2026-09-10. Calculations run in your browser; nothing you type is sent to a server.