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Body Fat Calculator Tool

Estimate body fat percentage from gender, height, weight, and circumference measurements using both the US Navy method and a BMI-based formula. Free tool showing fat mass, lean mass, and body composition category.

Last updated: 2026/10/16 Calculator Feedback & bug reports
Input
Men: at navel level. Women: at the narrowest point.
Measure horizontally around the narrowest part of the neck.
The US Navy method requires gender, height, waist, and neck (plus hip for women).
Results
US Navy Method
--%
--
BMI Method (Estimated)
--%
Estimated from BMI, age, and gender (when age is entered).
BMI
--
Estimated Fat Mass
--kg
Estimated Lean Mass
--kg
The body fat percentages here are general estimates derived from circumference measurements or BMI, not a medical diagnosis or advice. For accurate measurement, use a body composition analyzer or professional assessment. Always consult a doctor or specialist for health decisions.

How to Use

1

Enter gender and body data

Select your gender and enter height and weight. Entering age also shows a BMI-based estimate.

2

Enter measurements

Enter waist and neck (plus hip for women) measured with a tape. Measure the narrowest part of the neck, and the waist at navel level (narrowest point for women).

3

Calculate and review

Press "Calculate Body Fat" to see body fat % from the US Navy and BMI methods, plus fat mass, lean mass, and a body composition category.

4

Copy the results

Use the "Copy Results" button to copy the values for your records or to share.

About the Body Fat Calculator

Body fat percentage is the proportion of fat in your total body weight. Even without a body composition analyzer, this tool estimates it from tape measurements (waist, neck, hip) plus height and weight, using both the US Navy circumference method and a BMI-based formula. The values are estimates only, and all calculations run entirely in your browser. Your data is never sent to any server.

Features

  • Two Estimation MethodsEstimate body fat with both the US Navy circumference method and a BMI-based formula, side by side.
  • Fat & Lean MassAutomatically derive estimated fat mass (kg) and lean mass (kg) to understand your body composition.
  • Composition CategoryColor-coded categories such as Athletes, Average, and Obese based on gender-specific ranges.
  • Privacy ProtectedAll calculations happen in your browser. Your input data is never sent to servers.

Use Cases

  • Self-check body fat without a body composition analyzer
  • Set targets for dieting and body recomposition
  • Track progress during training or weight loss
  • Understand composition beyond BMI alone
  • Self-monitoring before a health checkup

FAQ

What is the US Navy circumference method?
It estimates body fat percentage from neck, waist, and height (with hip added for women). It works without a body composition analyzer and is widely used because it is quick and easy. It is an estimate and may differ from measured values.
How does it differ from the BMI-based estimate?
The BMI method (Deurenberg formula) estimates body fat from BMI, age, and gender. It needs no measurements but reflects individual differences in build and muscle mass less well. This tool shows both methods so you can compare them as a reference.
Where and how do I take the measurements?
Measure the neck at its narrowest point horizontally; the waist at navel level for men and at the narrowest point for women. Hip (women only) is measured at the largest part of the hips. Keep the tape level and snug but not tight.
How accurate is the estimated body fat percentage?
Circumference and BMI methods trade accuracy for convenience and can differ from analyzer measurements (e.g. DEXA) by a few percent. Use them to track trends over time, and seek professional measurement when accuracy matters.
Is my data safe, and is this medical advice?
All calculations run in your browser, and your input data is never sent to or stored on our servers. The results are general estimates, not a medical diagnosis or advice. Always consult a doctor or specialist for health and diet decisions.

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Related Guides

What Is Body Fat Percentage? How to Measure It, Targets by Sex and Age Learn what body fat percentage is from the ground up: how it differs from BMI, estimation methods such as bioelectrical impedance (Tanita-style) and the Navy circumference method, targets by sex and age, how home body composition scales work and their margins of error, and a healthy range. BMI vs Body Fat Percentage: The Difference, How to Calculate, and Why Both Matter Learn the difference between BMI and body fat percentage from the basics. BMI comes from height and weight, while body fat percentage is the share of fat in your body. See why a muscular person can have a high BMI but low body fat, the typical ranges, the limits of each, and why you should look at both.