Body fat percentage calculator
US Navy method estimate from your body circumferences.
Calculator inputs
Results
Enter your values and press “Calculate” to see the result.
In short
- What it calculates
- US Navy method estimate from your body circumferences.
- Formula used
Men:- Example
- Man of 75 kg, 178 cm, waist 85 cm and neck 38 cm:
Body fat calculator
BMI cannot tell muscle from fat; this method tries to, using body circumferences that better reflect where adipose tissue accumulates.
All you need is a flexible tape measure.
How it works
The method developed by the US Navy relates logarithms of the circumferences to height. For men it uses waist and neck; for women it adds the hips.
Formula
Men:
495 / (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450
Women:
495 / (1.29579 − 0.35004·log₁₀(waist + hip − neck) + 0.22100·log₁₀(height)) − 450
Worked example
Man of 75 kg, 178 cm, waist 85 cm and neck 38 cm:
Body fat: 17.9%
Fat mass: 13.4 kg
Lean mass: 61.6 kg
Explanation
The circumference method came from the Navy
The most widespread formula for estimating body fat with a tape measure comes from a United States Navy study in the 1980s. It was designed to screen recruits quickly and cheaply, not to give an exact figure to an individual. That origin explains both its convenience and its limits.
How far off it can be
Against reference methods such as densitometry, circumference formulas can be three or four percentage points out, and more in very lean or very muscular people. They work for tracking a trend; they do not support claiming an exact number.
How to measure so it is useful
Always at the same time, preferably fasted, with the tape snug but not tight, parallel to the floor and not compressing the skin. Consistency matters more than absolute accuracy: if you measure the same way each time, the trend will be reliable even if the value is not.
Bioimpedance scales
They estimate fat by passing a weak current, and the result depends heavily on hydration, time of day and whether you have eaten or trained. They give very different figures for the same person within a single day.
Frequently asked questions
How do I measure correctly?
Waist at navel height, neck just below the Adam’s apple and hips at their widest point. Do not pull the tape tight and breathe normally.
How accurate is it?
The margin is usually ±3 percentage points against a DEXA scan. That is enough to track changes over time.
How accurate are these formulas?
Within three or four points of laboratory methods, and less accurate in very lean or very muscular people. They are useful for tracking a trend.
Are bioimpedance scales reliable?
They depend heavily on hydration and time of day. They measure consistently if you always use them under the same conditions.
Need to calculate something else?
These tools are often used alongside this calculator.
BMI
Calculate your BMI and see the healthy weight range for your height.
Ideal weight
Four classic formulas plus the healthy range from BMI.
Calories
The calories you need for your goal, with the protein, fat and carb split.
Protein
Recommended grams of protein based on your weight and activity level.
BMR
The calories your body burns at complete rest, from two formulas.
TDEE
Calories you burn each day given your metabolism and activity level.