What is a body fat calculator?

A body fat calculator estimates what percentage of your total body weight is made up of body fat. This is different from body weight alone, because two people can weigh the same but have very different body compositions.

Body fat percentage is often used alongside other measurements such as weight, BMI and waist circumference to give a broader view of body composition.

This calculator uses the U.S. Navy body fat formula, which estimates body fat from circumference measurements rather than weight alone.

How to use this body fat calculator

Using the calculator is simple:

1. Select whether you are male or female
2. Choose your preferred unit: centimetres or inches
3. Enter your height
4. Enter your neck circumference
5. Enter your waist circumference
6. If you are female, also enter your hip circumference
7. View your estimated body fat percentage instantly

The result updates automatically as you type, so there is no need to press a calculate button.

What measurements do you need?

To use the U.S. Navy body fat formula, you need a tape measure and a few basic body measurements.

For men:

• height
• neck circumference
• waist circumference

For women:

• height
• neck circumference
• waist circumference
• hip circumference

For the best result, measure carefully and keep the tape level around the body without pulling it too tightly.

Body fat formula used

This calculator uses the U.S. Navy circumference method.

For men:

Body fat percentage is estimated from:

• height
• neck circumference
• waist circumference

For women:

Body fat percentage is estimated from:

• height
• neck circumference
• waist circumference
• hip circumference

The formula uses logarithms to turn those measurements into an estimated body fat percentage. Because it is an estimate rather than a direct scan, the result should be used as a practical guide, not a medical diagnosis.

Example body fat calculation

Here is a simple example for a man using centimetres:

• Height: 180 cm
• Neck: 40 cm
• Waist: 90 cm

Using the U.S. Navy formula, the estimated body fat percentage would typically fall in the mid-to-high teens, depending on the exact measurements used.

Example for a woman:

• Height: 165 cm
• Neck: 34 cm
• Waist: 75 cm
• Hips: 95 cm

Using the same method, the estimated body fat percentage may fall in the mid-20s, depending on the exact values.

These examples are illustrative only, but they show how body fat can be estimated from body measurements alone.

Body fat categories

Body fat categories vary slightly by source, but they are often grouped into broad ranges such as:

For men

• Essential fat
• Athletes
• Fitness
• Average
• Above average

For women

• Essential fat
• Athletes
• Fitness
• Average
• Above average

These ranges are only intended as general reference points. They are useful for context, but they do not replace advice from a qualified health professional.

Why body fat percentage matters

Body fat percentage can be useful because it gives more detail than body weight alone. It may help you:

• track changes in body composition
• compare progress over time
• understand how lean mass and fat mass differ
• add more context to your BMI or weight measurements
• set more realistic fitness goals

Someone can lose weight without major changes in body fat, or maintain a similar weight while improving body composition. That is why body fat percentage is often tracked separately.

Is the U.S. Navy method accurate?

The U.S. Navy formula is a widely used estimation method, but it is not perfect. The result depends heavily on taking measurements correctly.

It can be useful for:

• quick estimates
• regular progress tracking
• comparing results over time using the same method

It may be less accurate than methods such as:

• DEXA scans
• hydrostatic weighing
• professional body composition testing

Still, for a free online calculator, it offers a practical and simple estimate.

Tips for measuring correctly

To get the most reliable result:

• measure in a relaxed standing position
• keep the tape horizontal
• do not pull the tape too tight
• use the same tape measure each time
• measure under similar conditions when tracking progress
• recheck any number that looks unusual

Consistent measuring technique is often more important than chasing perfect precision.

Body fat calculator vs BMI

A body fat calculator and BMI calculator are not the same.

BMI uses height and weight to estimate whether someone is in a broad weight category.
Body fat percentage attempts to estimate how much of the body is fat.

BMI is quick and useful at population level, but it does not distinguish between fat and muscle. Body fat percentage can provide more detail, which is why many people use both together.

FAQs for Body Fat Calculator

How do I calculate body fat percentage?

You can estimate body fat percentage by using circumference measurements such as height, neck, waist and hips. This calculator uses the U.S. Navy formula to do that automatically.

Is this body fat calculator for men and women?

Yes. The calculator works for both men and women. For women, hip circumference is included in the formula as well.

What is a healthy body fat percentage?

There is no single ideal number for everyone. Healthy ranges can vary by age, sex and activity level. This calculator gives an estimate and a general category for reference.

Is the body fat result exact?

No. It is an estimate based on body measurements. It is useful for general guidance and progress tracking, but it is not a medical-grade assessment.

Can I use centimetres or inches?

Yes. This calculator supports both centimetres and inches.

Why does the women’s formula include hips?

The U.S. Navy formula for women uses hip circumference as part of the body fat estimate, while the men’s formula does not.

Other calculators available:
BMI
Macros
Calorie
Body Fat