Fitness calculator
Body Fat Percentage Calculator
Estimate body fat percentage from U.S. Navy tape measurements. Includes lean body mass and category ranges for male and female.
Body Fat Percentage
16.9%
How it works
The U.S. Navy tape method estimates body fat percentage from a few circumferences: height, neck, waist, and (for women) hips. Because it works from body shape instead of total weight, it picks up fat distribution that BMI cannot see.
The Navy method uses logarithmic formulas developed from regression analysis comparing tape measurements to hydrostatic weighing and other direct body fat assessment methods. Typical accuracy is ±3–4% compared to DEXA (dual-energy X-ray absorptiometry), the medical gold standard.
All measurements must be in centimeters for the formula. This calculator converts imperial (inches) automatically.
If the formula produces an unrealistic result (below 2% or above 60%), the calculator shows '—' instead. That almost always means a measurement was taken or entered wrong.
How to measure
- Neck: Measure horizontally just below the larynx (Adam's apple). The tape should sit snugly without compressing the skin.
- Waist (male): Measure at the level of the navel. Keep the tape level and avoid sucking in your stomach.
- Waist (female): Measure at the narrowest point between ribs and hips, typically just above the hip bones.
- Hips (female only): Measure at the widest point of the buttocks. Ensure the tape is level and snug but not compressing.
- Height: Measure barefoot, standing against a wall. Record in centimeters or inches as needed.
- Use a soft measuring tape (not a ruler). Take measurements twice to ensure consistency, and average the results if they differ.
Worked example
A male individual, 180 cm tall, with a waist circumference of 85 cm and neck circumference of 37 cm:
Difference: waist − neck = 85 − 37 = 48 cm
log₁₀(48) ≈ 1.681
log₁₀(180) ≈ 2.255
Denominator: 1.0324 − 0.19077(1.681) + 0.15456(2.255) ≈ 1.060
Body fat: 495 ÷ 1.060 − 450 ≈ 16.9%
Category: Fitness (14–17% for males)
Body fat categories
The following ranges are based on guidelines from the American Council on Exercise (ACE):
Essential fat is the minimum needed for vital organ function and overall health. It includes the lipids in your brain, nerves, and bone marrow.
The 'Average' category represents the typical body fat ranges for adults; these are not targets but descriptors of general population distribution.
- Male — Essential fat: 2–5%, Athletes: 6–13%, Fitness: 14–17%, Average: 18–24%, Obese: 25%+
- Female — Essential fat: 10–13%, Athletes: 14–20%, Fitness: 21–24%, Average: 25–31%, Obese: 32%+
Navy method vs. BMI
The Navy tape method and BMI are complementary tools that measure different aspects of body composition. BMI relates total weight to height and does not distinguish between muscle, bone, and fat. A very muscular person or athlete might have a 'high' BMI yet low body fat.
The Navy method estimates fat percentage from body shape, which makes it the better of the two for tracking composition changes during a training program. It is still an estimate with ±3–4% uncertainty; for a diagnostic measurement you need DEXA or hydrostatic weighing.
Run your numbers through the BMI calculator as well. The two readings together tell you more than either one alone.
Frequently asked questions
How accurate is the Navy tape method?
When measurements are taken correctly and consistently, the Navy method is typically within ±3–4% of body fat measured by DEXA (the medical gold standard). Accuracy depends on precise measurement technique and consistent tape tension. Small variations in how you take measurements can shift the result by 1–2%, so re-measure if results seem off.
What is ideal body fat?
There is no single ideal percentage; it depends on age, activity level, goals, and health. ACE lists 14–17% for men and 21–24% for women as fitness-level targets, with athletes running lower (6–13% and 14–20%, respectively). Very low body fat (under 5% for men or 10% for women) harms hormone function and health, so talk to a healthcare provider before chasing extreme numbers.
Do I need to enter my weight?
No, weight is optional. The calculator estimates body fat percentage from tape measurements alone. If you enter your weight, it also calculates fat mass (the actual weight of body fat) and lean body mass (muscle, bone, organs, etc.). These values require both the percentage and the total weight, so they show '—' if weight is blank.
Why does the result show '—'?
The calculator displays '—' when inputs are missing or when the formula produces an impossible result (below 2% or above 60%). This usually means the circumference measurements are inaccurate or inconsistent. Check that your waist and hip (for females) are larger than your neck, re-measure carefully with consistent tape tension, and try again.
This calculator is for informational and educational purposes only and is not medical advice. Its results are general estimates, not an individual assessment. Talk to a doctor, registered dietitian, or other qualified health professional before making decisions about your health, diet, or exercise.