Body Fat Calculator

Estimated body fat

31.6258

Computed from default inputs using graph `synth-body-fat-calculator`.

Waist

90 cm

Range: 30 - 250

Solve for Height

Height: 163.1777 for Estimated body fat 34.793

US Navy tape-measure body fat estimate in metric units (cm), sex-branched.

bodyFatPercent=\max\left(0,\min\left(70,\left(\begin{cases} {\frac{495}{\left(1.0324-0.19077\cdot\log_{10}\left(\max\left(1, waistCm- neckCm\right)\right)+0.15456\cdot\log_{10}\left( heightCm\right)\right)}}, &\quad{\text{if }\; isMale=1}\\{\frac{495}{\left(1.29579-0.35004\cdot\log_{10}\left(\max\left(1, waistCm+ hipCm- neckCm\right)\right)+0.221\cdot\log_{10}\left( heightCm\right)\right)}}, &\quad{\text{otherwise}}\end{cases}\right)-450\right)\right)

bodyFatPercentmax(0, min(70, (isMale == 1 ? 495 / (1.0324 - 0.19077 * log10(max(1, waistCm - neckCm)) + 0.15456 * log10(heightCm)) : 495 / (1.29579 - 0.35004 * log10(max(1, waistCm + hipCm - neckCm)) + 0.22100 * log10(heightCm))) - 450))

Estimated body fat decision comparison

item	value	note
Stress low	69.61	Height: 80
Downside	36.41	Height: 157.5
Base case	31.63	Height: 175
Upside	27.38	Height: 192.50000000000003
Stress high	16.1	Height: 250

Visual Analysis1 series8 points

Expanded chart built from the same sensitivity run as the table, so users can read the trend and verify the numbers in one place.

Trend

Downward

Min

28.3814

Max

69.6085

Insight

Estimated body fat shows a downward pattern, with a visible peak around 80 at 69.6085.

Visual response curve for Estimated body fat.

Health tools disclaimer: Educational estimates only, not medical advice, diagnosis, or treatment. For clinical decisions, dosing, or emergencies, follow guidance from US Department of Health & Human Services and a licensed professional in your jurisdiction.

Estimate body fat percentage from tape measurements using a Navy-style metric equation.

Body Fat Calculator turns Waist, Neck, Height, Hip, and Sex (1 = male, 0 = female) into Estimated body fat. Confirm the units and assumptions match your situation before relying on the result.

Body Fat Calculator produces a screening estimate, not a diagnosis. Measurements such as Waist, Neck, Height, Hip, and Sex (1 = male, 0 = female) translate into Estimated body fat, which is useful for tracking a trend over time or preparing questions for an appointment — not for deciding treatment, dosing, or urgency on its own.

Estimate quality tracks measurement quality: enter current values, use the units each input asks for, and describe the individual case rather than a population average. If a result would change medication use, urgent care timing, or a treatment decision, stop at the estimate and confirm the next step with a licensed professional.

Overwhelm from technical jargon

Start with the basic inputs only — advanced options can be explored once you understand the fundamentals. Important: Don't be discouraged if your results seem unfavorable — these tools help you plan, not judge.

Enter your values, then check the formula, scenarios, and FAQ to confirm the assumptions fit your case. For medical, financial, legal, or safety-critical decisions, treat the output as an estimate and verify it against the relevant professional standard.

World Health Organization. "Body mass index - BMI." WHO Regional Office for Europe, 2024.BMI classification thresholds: underweight <18.5, normal 18.5-24.9, overweight 25-29.9, obese ≥30
Centers for Disease Control and Prevention. "About Child & Teen BMI." CDC, 2024.Pediatric BMI uses age-sex-specific percentiles, not adult thresholds
Mifflin MD, St Jeor ST, et al. "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr. 1990;51(2):241-247.BMR formula: 10×weight(kg) + 6.25×height(cm) - 5×age - 161 (female) or +5 (male)
Institute of Medicine. "Weight Gain During Pregnancy: Reexamining the Guidelines." National Academies Press, 2009.Recommended pregnancy weight gain by pre-pregnancy BMI category

When is this health estimation context enough?
Use it when the result only depends on age, sex, height and no local rule changes the interpretation.

What should I record with the result?
Record the input values, reference population, measurement unit, activity estimate, output unit, and rounding rule used in the calculation.

When should I use a specialized modifier?
Use a specialized modifier when measurement units, reference range, age/sex context, and non-diagnostic limits materially changes how the same result should be explained.

Scenario	Inputs	Result	Interpretation
Navy tape estimate, adult male	Waist: 90 cm; Neck: 38 cm; Height: 175 cm	20.7% body fat	US Navy circumference formula (men): 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. Here: 495 ÷ (1.0324 − 0.19077 × log₁₀(52) + 0.15456 × log₁₀(175)) − 450 = 495 ÷ 1.05170 − 450 = 20.7%.
Waist measurement sensitivity	Waist: 85 cm vs 95 cm; Neck: 38 cm; Height: 175 cm	16.9% at 85 cm vs 24.1% at 95 cm	A 10 cm waist span moves the estimate 7.2 percentage points — about 0.7 points per centimetre — with neck and height held constant.
Measurement repeat check	First reading: 90 cm waist; Second reading: 91 cm waist; Same height/neck: 38 cm / 175 cm	20.7% vs 21.4%	One centimetre of tape-placement drift changes the estimate by 0.7 percentage points, so a single reading carries roughly that much measurement noise.

Measuring the waist, neck, or hip at a different location each time.

Comparing this tape estimate directly with a DEXA or scale-based body-fat result without noting the method.

Treating one rounded percentage as exact instead of checking the sensitivity table.

Verification & transparency

Verified methodology

Data & accuracy

Privacy & ethics

Primary output (Estimated body fat)

Calculator inputs

Mathematical model

Term Glossary

Reverse Solve

Formula and method

Computation graph

Estimated body fat decision comparison

Result chart

How to use this calculator

Sources & Standards

Verify this result