# Body fat calculator

> Body fat percentage can be estimated from tape measurements with the U.S. Navy method, or from BMI and age with the Deurenberg formula. A man who is 5 ft 11 in with a 36 in waist and a 15 in neck comes out near 20.8% body fat, the average range. Both methods are estimates and can miss by several percentage points.

Source: https://www.calterix.com/en-us/calculator/body-fat/ · Updated 11/06/2026 · en-US

## The two methods

The **U.S. Navy method** uses height and a few tape measurements. The military developed it to screen service members without lab equipment. Results are only as good as the tape work.

```
Men: body fat % = 86.010 × log(waist − neck) − 70.041 × log(height) + 36.76
Women: body fat % = 163.205 × log(waist + hip − neck) − 97.684 × log(height) − 78.387
```
All measures in inches, log base 10. Example (man): 71 in tall, 36 in waist, 15 in neck. Waist − neck = 21. Result: 20.8%.

The **Deurenberg formula** estimates fat from BMI, age, and sex. Muscular people often read too high, and older or sedentary people with a low BMI often read too low.

```
Body fat % = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4
sex = 1 for men, 0 for women
```
Example: man, 30 years old, 180 lb, 5 ft 11 in. BMI = 25.1. Body fat = 30.1 + 6.9 − 10.8 − 5.4 = 20.8%.

[BMI](https://www.calterix.com/en-us/calculator/bmi/) alone cannot separate fat from muscle, so the calculator offers both routes.

## Body fat percentage chart

| 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 range | 32% or higher | 25% or higher |

Descriptive categories from the American Council on Exercise (ACE). Not a diagnosis.

Essential fat is the minimum the body needs to function. Staying at that level for long carries health risks, so do not treat the chart as a goal without guidance from a professional.

## Accuracy and how to measure

- A DEXA scan or a lab hydrostatic test beats any formula. Tape and BMI methods can be off by several points.
- Measure the waist at the belly button, tape snug but not squeezing, after a normal exhale. Morning, before eating, is best.
- Use the same method each time and watch the trend. One number alone says little.
- The formulas are built for healthy adults. Pregnancy, elite athletes, and swelling from illness call for other methods.

For the weight range that matches your height, see the [ideal weight calculator](https://www.calterix.com/en-us/calculator/ideal-weight/). For energy needs, try the [BMR calculator](https://www.calterix.com/en-us/calculator/bmr/) or the [calorie calculator](https://www.calterix.com/en-us/calculator/calorie/).

## Frequently asked questions

### How do I calculate my body fat percentage?

Use the U.S. Navy method with height, waist, and neck (plus hips for women), or the BMI and age formula. Both give estimates. A DEXA scan is more accurate.

### What is a good body fat percentage?

By ACE ranges, average is 18 to 24% for men and 25 to 31% for women, and fitness is 14 to 17% and 21 to 24%. What is healthy for one person depends on age and health, so ask a doctor.

### How accurate is the Navy body fat method?

It works as a screening tool and for tracking change, but it can be off by several percentage points. Where the tape sits matters a lot.

### Where do I measure my waist and neck?

Wrap the tape around the waist at the belly button after a normal exhale, snug but not tight. Measure the neck just below the Adam's apple with the tape level. Use the same spots every time.

### Can I get body fat from BMI alone?

Yes, with the Deurenberg formula, but accuracy drops. BMI cannot separate muscle from fat, so lifters and older adults often get the least reliable numbers.

### Are smart scales accurate for body fat?

They can swing with hydration, time of day, and recent meals, and may miss by more than the tape methods. Weigh under the same conditions each time and look at trends.