Body Fat Calculator
Estimate your body fat percentage with a tape measure using the U.S. Navy method, or from height, weight and age if you don't have one handy. Add your weight to see fat mass, lean body mass and a goal weight that accounts for muscle loss, not just fat.
Measure the waist horizontally at the navel and the neck just below the Adam's apple. Add your weight to see fat mass, lean mass and a goal weight.
Body fat percentage chart
The American Council on Exercise (ACE) ranges are the most widely used reference. The calculator places your result on this scale.
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obese | 32%+ | 25%+ |
How the Navy method works
The U.S. Navy formula, also used across the Department of Defense, estimates body fat from circumference measurements and height. Waist size tracks abdominal fat; neck size roughly tracks frame and muscle. Women's equation adds the hips.
- 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
All measurements are in inches. The calculator converts from centimetres if you use metric.
Measuring correctly
- Use a flexible, non-stretch tape, snug but not compressing the skin.
- Neck: just below the larynx (Adam's apple), tape angled slightly down toward the front.
- Waist (men): horizontally at the navel, at the end of a normal breath out.
- Waist (women): at the narrowest point, usually just above the navel.
- Hips (women): at the widest part of the buttocks.
- Measure each site twice and average. Measure at the same time of day for tracking.
Comparing body fat methods
| Method | Typical accuracy | Notes |
|---|---|---|
| DEXA scan | Reference standard | Also maps lean mass by region; costs roughly $50–150 at a clinic |
| Skinfold calipers | ±3–4% (skilled tester) | Highly dependent on technique; 3- and 7-site versions |
| Navy tape method | ±3–4% | Free, repeatable, good for tracking trends |
| Smart scale (BIA) | Varies widely | Sensitive to hydration, meals and time of day |
| BMI-based estimate | Least precise | Can't distinguish muscle from fat |
Body fat on GLP-1 medications: why the goal weight table shows three answers
The standard way to compute a goal weight assumes you lose only fat and keep every pound of lean mass. That rarely happens. In body-composition substudies of the major trials, roughly a quarter of the weight lost on tirzepatide (SURMOUNT-1) and nearly two-fifths on semaglutide (STEP 1) was lean mass rather than fat. Those are averages, and lean mass includes more than muscle, but the point holds: if part of what you lose is lean tissue, you have to lose more total weight to reach the same body fat percentage.
That's why the calculator shows the goal weight under three assumptions. Strength training and adequate protein are the main levers for keeping your result closer to the “all fat” row. They're worth raising with your prescriber if you're starting a GLP-1. See our weight loss projector for trial-average timelines.
Frequently Asked Questions
How accurate is the Navy body fat calculator?
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Compared with lab methods like DEXA, circumference equations like the Navy method typically land within about 3 to 4 percentage points for most people, and are less accurate at the extremes. Very muscular people and people with a lot of abdominal fat are the most likely to get a misleading number. Measurement technique matters as much as the formula, so measure the same way each time.
What is a healthy body fat percentage?
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Using the American Council on Exercise ranges, 14–24% is typical of fit to average men and 21–31% of fit to average women. Essential fat, the minimum needed for normal function, is about 2–5% in men and 10–13% in women. Healthy ranges also shift somewhat with age.
What's the difference between body fat ratio and body fat percentage?
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They're used to mean the same thing: the share of your total body weight that is fat. A 200 lb person with 50 lb of fat has a body fat ratio, or percentage, of 25%.
How do I calculate lean body mass from body fat percentage?
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Multiply your weight by your body fat percentage to get fat mass, then subtract that from your weight. At 200 lb and 25% body fat: fat mass is 50 lb, lean body mass is 150 lb. The calculator does this automatically when you enter your weight.
Can I estimate body fat without measurements?
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Yes. The 'No measurements' option uses the Deurenberg equation, which estimates body fat from BMI, age and sex. It's a population average, so it can't tell muscle from fat and will overestimate body fat in muscular people. A tape measure gives a better estimate.
Is this the same as the Army body fat calculator?
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No. This uses the Navy circumference method from the Department of Defense. The Army moved to its own single-site, waist-based tape test in 2023, with different equations. Service members should use their branch's official current standard.
Medical disclaimer: Body fat calculators give estimates, not measurements. Results can differ from DEXA, hydrostatic weighing or a clinician's assessment by several percentage points. Use the number to track trends over time, not as a diagnosis. Not medical advice.