What is a healthy body fat percentage?

General guidelines: Men — Essential fat (2–5%), Athletes (6–13%), Fitness (14–17%), Acceptable (18–24%), Obese (25%+). Women — Essential fat (10–13%), Athletes (14–20%), Fitness (21–24%), Acceptable (25–31%), Obese (32%+). These ranges vary slightly by source.

How accurate is the Navy method?

Studies show the Navy method has a mean error of about 3–4% compared to DEXA scans. It tends to overestimate body fat in lean individuals and underestimate it in very overweight individuals. It is most reliable in the average fitness range.

How does body fat percentage differ from BMI?

BMI measures weight-to-height ratio and cannot distinguish muscle from fat. Body fat percentage directly estimates how much of your body weight is fat versus lean mass. Two people with the same BMI can have very different body fat percentages depending on their muscle mass.

How often should I measure body fat?

Measuring every 4–6 weeks is a good interval. More frequent measurements add noise from hydration and measurement inconsistency without providing meaningful signal. Always measure under the same conditions (morning, same time, same person measuring) for consistent comparisons.

Formula Guide

How to Calculate Body Fat Percentage (Navy Method)

The U.S. Navy body fat method estimates body fat percentage using simple tape measurements — no equipment beyond a flexible measuring tape required. While less accurate than DEXA scans or hydrostatic weighing, it is considerably more accessible and accurate enough for tracking trends over time. The formula was developed by the U.S. Navy to assess fitness standards and has been validated against underwater weighing.

Last updated: March 31, 2026

The Formula

Men:
  %BF = 495 ÷ (1.0324 − 0.19077×log₁₀(waist−neck) + 0.15456×log₁₀(height)) − 450

Women:
  %BF = 495 ÷ (1.29579 − 0.35004×log₁₀(waist+hip−neck) + 0.22100×log₁₀(height)) − 450

All measurements in centimetres. Waist measured at the navel (men) or narrowest point (women). Neck measured just below the larynx. Hip measured at the widest point (women only).

Variable Definitions

Symbol	Name	Description
waist	Waist Circumference	Measured at the navel for men; at the narrowest point of the torso for women, in cm
neck	Neck Circumference	Measured just below the larynx (Adam's apple), in cm
hip	Hip Circumference	Women only — measured at the widest point of the hips/buttocks, in cm
height	Height	Standing height in centimetres

Step-by-Step Example

A man with the following measurements: waist 90 cm, neck 40 cm, height 180 cm.

Given

Waist:90 cmNeck:40 cmHeight:180 cm

Solution

1
Calculate waist − neck: 90 − 40 = 50 cm
2
Calculate log₁₀(50): log₁₀(50) ≈ 1.6990
3
Calculate log₁₀(180): log₁₀(180) ≈ 2.2553
4
Calculate the denominator: 1.0324 − (0.19077 × 1.6990) + (0.15456 × 2.2553)
5
Expand: 1.0324 − 0.3241 + 0.3485 = 1.0568
6
Divide 495 by the denominator: 495 ÷ 1.0568 = 468.4
7
Subtract 450: 468.4 − 450 = 18.4%

Estimated body fat is 18.4%, which falls in the Fitness category for men (14–17% is Fitness, 18–24% is Acceptable).

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Common Mistakes to Avoid

Taking measurements incorrectly — the waist measurement must be at the navel for men, not the narrowest point. Even a 1 cm error can shift the result by 1–2%.

Forgetting to include the hip measurement for women — the women's formula requires three measurements (waist, neck, hip).

Using inches instead of centimetres — the formula is calibrated for centimetres. Multiply inches by 2.54 to convert.

Expecting laboratory-level precision — the Navy method has a standard error of ±3–4% body fat. It is useful for tracking changes, not for exact values.

Frequently Asked Questions

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