Calculator
What the Body Fat Calculator does
Body Fat Calculator: calculates Body Fat % and Category from Sex, Height and Neck. Example: sex Male, height 170 cm and neck 38 cm gives body fat % 17.8.
Give the Body Fat Calculator your Sex, Height, Neck and Waist and it works out Body Fat % and Category. Everything recomputes live, which makes it easy to test a few scenarios in a row.
Knowing how a figure is derived makes it much easier to interpret sensibly. The Body Fat Calculator exists to take that particular chore off your hands.
Nothing you enter about your body is sent anywhere or stored.
The field table, the method and a worked example are documented after the tool for anyone who wants to check the working.
What do the Body Fat Calculator fields mean?
The Body Fat Calculator uses 5 inputs. It opens with a complete example loaded, which is usually the quickest way to understand what a field means.
| Field | What to enter | Default |
|---|---|---|
| Sex | choose from Male or Female | Male |
| Height | measured in cm; accepts 120 to 230 | 170 |
| Neck | measured in cm; accepts 20 to 60 | 38 |
| Waist | measured in cm; accepts 40 to 200 | 85 |
| Hip (women) | measured in cm; accepts 40 to 200 | 95 |
How does the Body Fat Calculator work?
Each output is derived from the inputs above in a single pass; there is no hidden state carried between runs, so the same inputs always give the same calculation.
Validation runs before the calculation, which is why a mistyped value shows an error rather than a plausible-looking result.
Worked example
These are the values the Body Fat Calculator loads by default, and the result it produces from them. The numbers below come straight from the default inputs, so you can verify them against the live tool.
| Sex | Male |
|---|---|
| Height | 170 cm |
| Neck | 38 cm |
| Waist | 85 cm |
| Hip (women) | 95 cm |
| Body Fat % | 17.8 |
|---|---|
| Category | Fitness |
| What this means | Estimated body fat is 17.8% (Fitness). U.S. Navy tape method, good for tracking trends, not lab accuracy. |
Read next: Understanding BMI: What the Number Measures, and What It Misses
How to use it
- Pick a value for Sex: the options are Male or Female.
- Put Height in cm (120 to 230).
- Key in Neck in cm (20 to 60).
- Fill in Waist in cm (40 to 200).
- Type Hip (women) in cm (40 to 200).
- Results update continuously rather than on submit.
- Check Body Fat %, Category and What this means on the right.
- To keep the result, either copy the link or print the page. Both preserve what is on screen.
What this tool does not do
- These formulas come from population averages and cannot account for your medical history.
- This is a screening estimate, not a diagnosis.
- The tool answers exactly the question it is given; it cannot know the context around your numbers.
- The tool trusts your numbers completely, so a mis-keyed digit propagates straight through.
Frequently asked questions
Enter Height in cm, Neck in cm, Waist in cm and Hip (women) in cm. Every input names its unit, and every output does too, which removes the usual source of error.
Height accepts 120 to 230 cm. Go outside it and you get an error against that specific field instead of a misleading number.
With the values loaded when the page opens, body fat % comes out as 17.8. Try changing one value. The answer refreshes without a page reload.
No record is kept. We never receive what you type, so there is nothing on our side to retain.
It is free with no conditions: no sign-up, and no limit on how often you use it.
Accurate to the published method. Whether the published method suits your circumstances is a question for someone who knows your history.