How do you calculate body fat percentage with the U.S. Navy method?

The Navy method uses neck, waist, and (for women) hip circumferences plus height—no calipers required. Metric male example (this page default): 178 cm, waist 96 cm, neck 50 cm → BF% ≈ 15.7% via 495/(1.0324 − 0.19077×log₁₀(waist−neck) + 0.15456×log₁₀(height)) − 450. Fat mass = 70 kg × 15.7% = 11 kg; lean = 59 kg. Measure to ¼ in (0.5 cm) for best accuracy.

What is a healthy body fat percentage for men and women?

ACE categories: Men — Athletes 6–13%, Fitness 14–17%, Average 18–24%, Obese 25%+. Women — Athletes 14–20%, Fitness 21–24%, Average 25–31%, Obese 32%+. Default male result 15.7% = “Fitness”. Essential fat (~2–5% men, ~10–13% women) is required for hormones and organs—staying below essential levels needs medical supervision.

Navy method vs BMI body fat formula — which should I trust?

Prefer Navy when you have reliable tape measurements—it uses shape, not just weight. Same default male: Navy 15.7% vs BMI-based 16.1% (BMI 22.1, formula 1.20×BMI + 0.23×age − 16.2). They often differ by 1–3 points. Athletes with high BMI may read “fat” on BMI method; Navy can be better if waist is lean.

How do I measure neck, waist, and hip for the Navy calculator?

Neck: below Adam’s apple, tape angled slightly downward. Men’s waist: horizontal at navel, relaxed, no sucking in. Women’s waist: narrowest point. Women’s hip: widest glute/hip circumference. Example error: 1 cm waist mistake can shift BF% ~1–2 points. Morning, fasted, same tape position each time.

Why do women need hip measurement?

The female Navy equation uses log₁₀(waist + hip − neck) because women store more lower-body fat. Example — 60 kg, 165 cm, neck 34 cm, waist 68 cm, hip 95 cm → about 22.8% (Fitness), fat mass 13.7 kg. Without hip, the formula is invalid.

What is ideal body fat by age (Jackson & Pollock)?

Population reference ideals, not prescriptions: men age 25 → ~10.5% in our table; women age 30 → ~19.3%. Default male at 15.7% vs ideal 10.5% → about 3.7 kg fat to reach ideal at current weight (if only fat changes). Real cuts lose some lean too—use as a rough target.

What is the difference between body fat mass and lean body mass?

Fat mass = weight × BF%. Lean mass = weight − fat mass (includes muscle, bone, water, organs). Default: 11 kg fat + 59 kg lean = 70 kg total. “Lean” is not pure muscle—hydration can swing lean mass ±1–2 kg day to day on scales.

How accurate is the Navy body fat calculator?

Well-measured Navy vs DEXA is often within ~±3–5% for most adults. Errors come from loose tape, wrong waist site, or post-meal bloating. BMI method error can exceed Navy when BMI is misleading. For legal/military body fat, use official tape rules (see our Army body fat calculator).

US units example: 5′10″, 160 lb, neck 15″, waist 34″

Navy BF% ≈ 17.5% (Fitness), BMI method 18.2%, fat mass 12.7 kg (28.0 lb). Waist 34″ vs default metric waist 96 cm (~38″) — each inch on waist moves BF% roughly 1–2 points for similar builds.

Can I track body composition changes over time?

Yes—log Navy BF% every 4–8 weeks with the same tape protocol, then plug start/end into our body composition change calculator for Δ fat and Δ lean mass. Example: drop from 15.7% toward 0% by tightening waist from 96 cm to 78 cm (same person model) shows how measurement drives the estimate.

What health risks are linked to high body fat?

Higher body fat—especially visceral (waist-driven)—associates with type 2 diabetes, hypertension, sleep apnea, and cardiovascular disease in population studies. Category “Obese” (men 25%+, women 32%+) is a screening flag, not a diagnosis. Discuss sudden gains or losses with a clinician.

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U.S. Navy · BMI method

Body Fat Calculator — Navy Method & Body Fat Percentage

Free body fat calculator using the U.S. Navy tape method (neck, waist, hip) plus a BMI-based estimate. Get body fat %, fat mass, lean mass, ACE category, and Jackson–Pollock ideal BF—in lb/kg or metric/cm.

Last updated: May 24, 2026

Navy + BMI formulas side-by-side

Fat mass, lean mass, ideal BF target

ACE categories for men and women

Tracking changes? Body composition change calculator

Body Fat Calculator

U.S. Navy tape method + BMI estimate · fat & lean mass

Unit system

Gender

Age

Weight (kg)

Height (cm)

Neck (cm)

Waist (cm)

Body fat (U.S. Navy)

15.7%

Fitness

BMI method

16.1%

BMI

22.1

Fat mass

11 kg

Lean mass

59 kg

Ideal BF (Jackson & Pollock, age 25)

10.5% · ~3.7 kg fat to reach ideal at current weight

Tape estimates only — measure to ¼ in (0.5 cm); same protocol each time.

What This Body Fat Calculator Shows

U.S. Navy BF%

15.7%

Fitness

Mass split

11 kg fat · 59 kg lean

70 kg total · male default

BMI method

16.1%

BMI 22.1 · age 25

Quick examples

Male metric default

15.7%

Female 60 kg

22.8%

US 5′10″ 160 lb

17.5%

Leaner waist 78 cm

Formulas & reference tables

Metric male walkthrough

waist−neck = 96−50 = 46 cm → Navy BF% ≈ 15.7% · fat mass ≈ 11 kg · lean ≈ 59 kg

U.S. Navy equations

Group	Formula
Male (US inches)	BF% = 86.010×log₁₀(waist − neck) − 70.041×log₁₀(height) + 36.76
Female (US inches)	BF% = 163.205×log₁₀(waist + hip − neck) − 97.684×log₁₀(height) − 78.387
Male (metric cm)	BF% = 495 / (1.0324 − 0.19077×log₁₀(waist − neck) + 0.15456×log₁₀(height)) − 450
Female (metric cm)	BF% = 495 / (1.29579 − 0.35004×log₁₀(waist + hip − neck) + 0.22100×log₁₀(height)) − 450

BMI-based body fat %

Group	Formula
Adult male (18+)	BF% = 1.20 × BMI + 0.23 × age − 16.2
Adult female (18+)	BF% = 1.20 × BMI + 0.23 × age − 5.4
Boy (<18)	BF% = 1.51 × BMI − 0.70 × age − 2.2
Girl (<18)	BF% = 1.51 × BMI − 0.70 × age + 1.4

ACE categories — men

Essential fat	2–5%
Athletes	6–13%
Fitness	14–17%
Average	18–24%
Obese	25%+

ACE categories — women

Essential fat	10–13%
Athletes	14–20%
Fitness	21–24%
Average	25–31%
Obese	32%+

Ideal body fat by age (Jackson & Pollock)

Age	Men	Women
20–22	8.5%	17.7%
23–27	10.5%	18.4%
28–32	12.7%	19.3%
33–37	13.7%	21.5%
38–42	15.3%	22.2%
43–47	16.4%	22.9%
48–52	18.9%	25.2%
53+	20.9%	26.3%

How to measure

Neck: Below the larynx (Adam’s apple); tape sloping slightly down at the front. Do not flare neck.
Waist (men): Horizontal at navel level. Do not suck in stomach.
Waist (women): Narrowest horizontal width (usually above navel).
Hip (women): Largest horizontal circumference at buttocks/hips — required for Navy female formula.
Accuracy: Measure to nearest ¼ in (0.5 cm). Same time of day, relaxed posture, flexible tape.

Limitations

Navy equations estimate fat from circumferences — error ±3–5% vs DEXA when measured well
Very muscular or obese individuals can sit outside validated ranges
BMI method ignores fat distribution and can misclassify athletes
Pregnancy, edema, and scoliosis distort waist/neck measures
Not for clinical diagnosis — use with trend photos and strength data

References

Hodgdon & Beckett, 1984 — U.S. Navy body fat prediction from circumferences
ACE — Body fat categories

Worked examples

Default male

178 cm · 70 kg · waist 96 cm

15.7% Navy

11 kg fat · 59 kg lean

Female

165 cm · 60 kg

22.8%

Fitness

US male

5′10″ · 160 lb · waist 34″

17.5%

BMI method 18.2%

Frequently Asked Questions

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