Result
- CategoryFitnessHealthy
- Navy methodtape: neck + waist (+ hip for women)17.0%
- Jackson-Pollock 3-sitebody density = 1.06770 g/cm³ (Siri eq.)13.6%
- BMI method (Deurenberg)roughest; uses BMI + age + sex20.1%
- Fat mass12.8 kg
- Lean mass62.2 kg
- BMI24.5
How to use this calculator
- Pick units and your sex.
- Measure your neck just below the larynx, parallel to the floor.
- Measure your waist at the navel, relaxed (not sucked in).
- For women: also measure the widest part of your hips.
- Take measurements in the morning, before eating.
About this tool
The US Navy body-fat formula is one of the most accessible methods that doesn't require special equipment — just a tape measure. It uses the difference between waist and neck (men) or waist+hip vs neck (women) along with height to estimate body fat percentage. Accuracy is within ±3% of DEXA scans for most people, but worse for very lean or very heavy individuals. The Deurenberg BMI method is even rougher (just BMI + age + sex) — included for comparison. For serious training or medical decisions, get a DEXA scan or hydrostatic weighing.
What this calculator does
Estimates your body fat percentage from tape-measure circumferences using the US Navy method (Hodgdon & Beckett 1984), and cross-checks it against the Deurenberg BMI formula. Returns the percentage, the ACE/ACSM fitness category (essential / athlete / fitness / average / obese), and derived fat-mass and lean-mass figures so you have a complete body-composition snapshot from a tape measure alone.
How it works — the formula
Men: %BF = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
Women: %BF = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387All measurements in inches. The formulas were derived from hydrodensitometry data on 1,025 active-duty Navy personnel (Hodgdon & Beckett, 1984) and remain the US Navy standard for body-composition screening. The Deurenberg BMI cross-check uses %BF = 1.20·BMI + 0.23·age − 10.8·sex − 5.4, where sex = 1 (male) / 0 (female).
Worked examples
- Inputs:
- sex = male, waist = 34 in, neck = 16 in, height = 70 in
- Output:
- 86.010·log₁₀(18) − 70.041·log₁₀(70) + 36.76 ≈ 15.5% → Fitness (ACE male 14–18%)
Fat mass on 75 kg ≈ 11.6 kg; lean mass ≈ 63.4 kg.
- Inputs:
- sex = female, waist = 28 in, hip = 38 in, neck = 13 in, height = 65 in
- Output:
- 163.205·log₁₀(53) − 97.684·log₁₀(65) − 78.387 ≈ 25.9% → Average (ACE female 25–32%)
- Inputs:
- BMI = 25, age = 35, male
- Output:
- 1.20·25 + 0.23·35 − 10.8·1 − 5.4 ≈ 21.85% — used as cross-check; less accurate than tape method
When to use this vs other tools
Body fat percentage is one of several body-composition signals. Pair it with these tools depending on what decision you are trying to make.
- BMI Calculator
You only have height and weight available — BMI is the population-level proxy when body-fat measurements are not possible.
- Lean Body Mass Calculator
You want to track lean mass directly (e.g. for cutting while preserving muscle) instead of fat percentage.
- Waist-to-Hip Ratio Calculator
You want to assess cardiovascular risk from fat distribution — WHO cutoffs target central adiposity, which body fat % alone does not.
- BMR Calculator
You have a measured body fat % and want a more accurate BMR via Katch-McArdle (uses lean body mass instead of total weight).
Authority note
The Hodgdon-Beckett circumference formulas are the official US Navy body-composition standard used in active-duty fitness assessments and have been validated against hydrodensitometry on over a thousand service members. Category cutoffs follow the American Council on Exercise / ACSM consensus ranges.
Limitations
- Tape positioning matters: a 1 cm waist-tape error can shift the result by ~1–2 percentage points. Take three measurements per site, in the morning before eating, and average them.
- Under-estimates body fat in very lean individuals (essential-fat range) and over-estimates in obese individuals — the Navy formula was derived on active-duty service members, a relatively narrow body-composition range.
- Not validated for pregnant women, children under 18, lactating women, or people with significant edema.
- Cannot distinguish visceral (intra-abdominal) fat from subcutaneous fat. For cardiovascular-risk assessment, supplement with a waist-to-height or waist-to-hip ratio.
- For training, medical, or research decisions, prefer DEXA, BodPod (air-displacement plethysmography), or hydrostatic weighing — they directly measure body composition rather than estimating it.
Tape-measure body-fat estimates are screening tools, not medical-grade. This calculator does not provide medical advice — consult a clinician for clinical body-composition assessment.