Body Fat Calculator

Use simple body measurements to estimate body fat percentage and lean-mass breakdown when you do not have access to a lab test.

Choose the formula set that matches your profile.
Enter body weight in kilograms.
Enter height in centimeters.
Enter neck circumference in centimeters.
Enter waist circumference in centimeters.
Required and must be greater than zero for female estimates.

Estimated body fat

17.3%

Estimated lean mass62
Estimated fat mass13
Formula Formula Assumptions 4 Example Example Sources 2 Last updated Mar 10, 2026
Inputs stay in the browser unless a future feature explicitly tells you otherwise. Use this as an estimate and validate important decisions with a qualified professional.

How to use this body fat calculator

  1. Select sex

    Choose male or female so the correct formula is applied.

  2. Enter weight

    Enter your body weight in the weight field.

  3. Enter height

    Enter your standing height in the height field.

  4. Enter circumferences

    Measure and enter your neck and waist circumferences; if female, also enter hip circumference.

  5. Review results

    Check your estimated body fat percentage along with the lean mass and fat mass breakdown.

Methodology

How this body fat calculator works

This body fat calculator uses height and circumference measurements to estimate body fat percentage from a tape-measure formula. It is helpful when you want a more body-composition-focused estimate than BMI provides, especially if you track changes over time with the same measurement method.

Formula
Entered measurements are converted to inches internally. 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) − 78.387
%BF Estimated body fat percentage
waist Waist circumference entered in centimetres and converted to inches internally; measured at the navel for men or the narrowest point for women
neck Neck circumference entered in centimetres and converted to inches internally; measured just below the larynx
hip Hip circumference entered in centimetres and converted to inches internally at the widest point (women only)
height Standing height entered in centimetres and converted to inches internally
log₁₀ Common (base-10) logarithm
Example

A male who is 180 cm tall with an 85 cm waist and a 38 cm neck is first converted to inch inputs for the U.S. Navy equation: height ≈ 70.87 in, waist ≈ 33.46 in, neck ≈ 14.96 in. %BF = 86.010 × log₁₀(33.46 − 14.96) − 70.041 × log₁₀(70.87) + 36.76 ≈ 16.2% body fat. If he weighs 82 kg, estimated fat mass is about 13.3 kg and lean mass is about 68.7 kg.

A female who is 168 cm tall, weighs 65 kg, and has a 34 cm neck, 72 cm waist, and 98 cm hip would estimate body fat at roughly 25.9%. That gives an estimated fat mass of about 16.8 kg and lean mass of about 48.2 kg, placing her within the commonly cited healthy range for women.

A male who is 175 cm tall, weighs 90 kg, and has a 40 cm neck and 95 cm waist would estimate body fat at roughly 22.9%. That gives an estimated fat mass of about 20.6 kg and lean mass of about 69.4 kg, suggesting that a meaningful portion of his weight is fat tissue rather than muscle.

Assumptions
  • ✓ Measurement quality matters a lot, so inconsistent tape placement can change the result more than people expect.
  • ✓ The estimate is based on the U.S. Navy circumference method, a practical field formula, not a direct body-composition test such as DEXA or hydrostatic weighing.
  • ✓ Trends over time are often more useful than one isolated result.
  • ✓ The formula was validated primarily on military populations and may be less accurate at extreme body-fat levels.
Notes
  • Take measurements under similar conditions each time, ideally at the same time of day, to improve comparability.
  • Use the result as a practical estimate and pair it with other markers like strength, waist trend, and health guidance when needed.
  • The U.S. Navy method is a circumference-based screening estimate; individual accuracy varies with body shape, measurement consistency, and population.
Sources
  1. Body Composition and Physical Performance — U.S. Navy circumference equations — circumference-based body-composition method context
  2. Hodgdon and Beckett — Navy body circumference report — historical U.S. Navy body-fat equation source

What is body fat percentage?

Body fat percentage is the proportion of your total body weight that is made up of adipose (fat) tissue. It is a more informative metric than body weight alone because two people at the same weight can have very different amounts of muscle and fat. Essential fat — the minimum needed for normal physiological function — is roughly 2 to 5 percent in men and 10 to 13 percent in women. Athletes often carry 6 to 13 percent (men) or 14 to 20 percent (women), while ranges commonly described as healthy for the general population sit around 14 to 24 percent for men and 21 to 31 percent for women. Values above those ranges are associated with increased risk for metabolic conditions, though individual health depends on many factors beyond a single number. Tracking body fat percentage over time can reveal changes in body composition that scale weight alone would miss, such as gaining muscle while losing fat.

How to take accurate tape measurements

The accuracy of a circumference-based body fat estimate depends almost entirely on how consistently you take the measurements. For the neck, wrap the tape just below the larynx (Adam's apple) and keep it level around the circumference without compressing the skin. For the waist, men should measure at the navel while standing relaxed with a normal breath; women should measure at the narrowest point of the torso. For the hip measurement required in the female formula, place the tape at the widest point of the buttocks. In all cases, keep the tape snug but not tight, ensure it is horizontal and not twisted, and take two readings to confirm consistency. Measure at the same time of day under similar conditions — morning before eating is a common choice — to reduce variability from bloating or hydration changes.

Body fat calculator FAQs

Is this more useful than BMI?

It can be, because it attempts to estimate body composition rather than relying only on height and weight.

Why do tape measurements matter so much?

Because the formula depends directly on those measurements, even small errors in neck, waist, or hip placement can move the result noticeably.

Can I compare results over time?

Yes. The calculator is often most useful for tracking trends when you measure consistently from week to week or month to month.

Is this as accurate as a body scan?

No. It is a practical estimate, not a laboratory-grade body-composition test.

Why does the formula differ by sex?

Men and women store fat in different patterns. The female formula adds hip circumference because women typically carry more subcutaneous fat around the hips and thighs, which changes the relationship between circumferences and body fat.

Written by Jan Křenek Founder and health calculator author
Reviewed by DigitSum Methodology Review Health formula verification
Last updated Mar 10, 2026

Use this as an estimate and validate important decisions with a qualified professional.

Inputs stay in the browser unless a future feature explicitly tells you otherwise.