Body Fat Calculator
US Navy method: body fat percentage from tape measurements
Free Body Fat Calculator – US Navy Method
Body fat percentage, category and lean mass from a tape measure
This body fat calculator uses the US Navy method, the tape-measure formula developed for the Navy's fitness assessments and still one of the most reliable no-equipment estimates. BMI tells you about your weight, but not how much of it is fat versus muscle — the navy body fat calculator fills that gap. Enter your gender, height, neck and waist (plus hip for women); the calculator returns your body fat percentage, your category on the ACE body fat chart and, if you add your weight, your fat mass and lean body mass. The method has a typical margin of ±3–5%, so measure the same way each time and track the trend rather than a single number.
Features
US Navy Method
The widely used tape-measure formula, no scales or gadgets needed.
Gender-Specific
Separate formulas and categories for men and women.
Fat & Lean Mass
Add your weight to see estimated fat mass and lean body mass.
Private & Free
All measurements stay in your browser and are never uploaded.
US Navy Method, Body Fat Chart & Formula
How to measure (US Navy method)
- Neck: just below the larynx, tape sloping slightly down to the front
- Waist — men: at the navel; women: at the narrowest point
- Hip (women only): at the widest point
- Tape snug, not tight; measure in the morning before eating
Body fat percentage chart (ACE)
- Essential fat — Men 2–5% · Women 10–13%
- Athletes — Men 6–13% · Women 14–20%
- Fitness — Men 14–17% · Women 21–24%
- Average — Men 18–24% · Women 25–31%
- Obese — Men 25%+ · Women 32%+
US Navy formula
- Men: 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
- Women: 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
- Measurements in inches; the calculator converts cm automatically
- Fat mass = weight × body fat % · Lean mass = weight − fat mass
Worked examples
- Man, 180 cm, neck 38 cm, waist 88 cm → ≈ 18% body fat (Average)
- Woman, 165 cm, neck 33 cm, waist 74 cm, hip 96 cm → ≈ 26% (Average)
- At 80 kg and 18%: fat mass ≈ 14.4 kg, lean mass ≈ 65.6 kg
Guides
- What Is BMI and How Is It Calculated?Why BMI and body fat percentage tell different stories
- How to Calculate Your Daily Calorie Needs (TDEE)Turn your body composition into a calorie target
Frequently Asked Questions
How do I measure correctly?
Use a soft tape measure. Neck: below the larynx, sloping slightly down to the front. Waist: at the navel for men, at the narrowest point for women. Hip (women): at the widest point. Keep the tape snug but not tight.
How accurate is the US Navy method?
Compared to gold-standard methods like DEXA, the tape method has a typical margin of ±3–5%. It can under- or overestimate for very muscular or very lean bodies, so it is best for tracking change over time.
What is a healthy body fat percentage?
By ACE standards, fitness range is about 14–17% for men and 21–24% for women, while the average range is 18–24% for men and 25–31% for women. Essential fat is 2–5% for men and 10–13% for women.
Is body fat better than BMI?
They measure different things. BMI is a quick weight-for-height ratio, while body fat percentage reflects composition. Using both gives a fuller picture.
How does the navy body fat calculator work?
It applies the US Navy circumference formula: your neck and waist (plus hip for women) measurements are combined with your height in a logarithmic equation that estimates body fat percentage. The result is then placed on the ACE body fat chart and, with your weight, split into fat mass and lean mass.
How often should I measure body fat?
Every 2–4 weeks is enough. Measure at the same time of day, in the same spots and with the same tape, and compare the trend. Day-to-day changes are mostly water and measurement noise, not real fat loss or gain.