Your measurements
Use a relaxed posture and a non-stretch tape. See where to measure ↓
Age checks adult eligibility; weight is used for mass estimates. Neither changes the body fat percentage formula.
Check your abdomen or waist measurement and selected units.
Fitness · reference category
Classic U.S. Navy method
- Fat mass
- 14.3 kg
- Lean body mass
- 68.7 kg
Lean body mass includes muscle, water, bone and organs. It is not a muscle-mass measurement.
An estimate, not a diagnosis or an official military assessment. One decimal place is display precision, not measurement accuracy.
Your body composition
Estimated fat: 17.3% · Fitness (14.3 kg).
| Component | Share | Mass |
|---|---|---|
| Fat | 17.3% | 14.3 kg |
| Lean mass | 82.7% | 68.7 kg |
Colored bands follow the selected sex. The marker shows your estimated percentage on a linear 0–100% scale; the table highlights its category. These reference categories are not a diagnosis, a performance assessment or personal targets. Essential fat is not a recommended weight-loss goal.
Body fat percentage categories
Based on the American Council on Exercise (ACE) reference chart. [4] “Athletes” and “Fitness” are category names, not proof of athletic ability. These ranges do not adjust for age.
| Category | Male | Female |
|---|---|---|
| Below essential range | <2% | <10% |
| Essential fat | 2–<6% | 10–<14% |
| Athletes | 6–<14% | 14–<21% |
| Fitness | 14–<18% | 21–<25% |
| Average | 18–<25% | 25–<32% |
| Obese | ≥25% | ≥32% |
ACE publishes whole-number ranges (for example, male Fitness: 14–17%). Here each band extends to the next category’s starting value, so decimal results have no gaps. The category uses the displayed percentage rounded to one decimal. “Below essential range” is an added flag for estimates below the chart’s minimum; recheck your measurements. Near a boundary, estimation error may change the category.
How to take the measurements
Measure directly against the skin without compressing it. Keep the abdomen relaxed and read the tape after a normal exhalation. The required sites differ between the two equations. [2]
| Measurement | Technique |
|---|---|
| Height | Stand upright without shoes and measure from the floor to the top of your head. |
| Neck | Measure just below the larynx, avoiding the Adam’s apple. Keep shoulders relaxed. |
| Male abdomen | Run the tape horizontally around the abdomen at the belly button. |
| Female waist | Measure the smallest natural waist circumference, rather than automatically measuring at the belly button. |
| Female hips | Measure horizontally around the widest part of the buttocks. |
Repeat each measurement to check consistency. Use the same sites and technique when comparing results over time; small tape-placement changes can alter the estimate.
How body fat percentage is calculated
This tool uses the classic circumference equations associated with Hodgdon and Beckett’s Navy research. The direct-percentage coefficients below are documented in the U.S. Coast Guard’s 2022 body-composition instructions. [1] All lengths in these equations must be in inches; metric inputs are divided by 2.54 first.
Male equation
Body fat (%) = 86.010 × log₁₀(abdomen − neck) − 70.041 × log₁₀(height) + 36.76
Female equation
Body fat (%) = 163.205 × log₁₀(waist + hips − neck) − 97.684 × log₁₀(height) − 78.387
log₁₀ means the base-10 logarithm. The combined circumference inside it must be positive. The calculator keeps full precision internally and rounds the displayed percentage to one decimal place. It does not apply military tape-rounding rules or pass/fail standards.
Convert percentage into mass
Fat mass = weight × body fat (%) ÷ 100
Lean body mass = weight − fat mass
Weight may be in kilograms or pounds as long as the mass outputs use the same unit. Changing weight alone changes the two mass estimates but not the circumference-based percentage. Age is not a term in these equations.
Worked example
For the male equation, take height 70 in, abdomen 34 in, neck 15 in and weight 170 lb:
| Step | Calculation |
|---|---|
| Circumference difference | 34 − 15 = 19 in |
| Body fat | 86.010 × log₁₀(19) − 70.041 × log₁₀(70) + 36.76 ≈ 17.5% |
| Fat mass | 170 × unrounded percentage ÷ 100 ≈ 29.8 lb |
| Lean body mass | 170 − unrounded fat mass ≈ 140.2 lb |
What the result can and cannot tell you
The result estimates how much of total body weight is fat. It does not measure visceral fat, diagnose a health condition, or show muscle distribution. A comparison with DXA in 609 fit U.S. Marines found individual errors and systematic differences between circumference estimates and DXA. The authors did not consider circumference estimates research-grade body-composition data. [3]
Body shape, muscularity and measurement technique can affect the estimate. There is no single guaranteed error margin for every visitor. A change in this calculator’s result does not prove an equal change in actual body fat.
This adult tool is not intended for children, pregnancy, or situations where swelling or altered anatomy makes circumference measurements unrepresentative. If a body-composition result will guide medical care, discuss an appropriate assessment with a qualified clinician.
Input limits are software checks, not healthy ranges or validated population limits. Mathematically impossible percentages are rejected instead of being silently capped.
Methodology and sources
Published by CalculatorsForMe. Method and implementation updated . This page explains a published estimation method; it has not been independently reviewed by a medical professional.
- U.S. Coast Guard — Body Composition, COMDTINST 1020.8I (2022, PDF) . Source for the male and female direct-percentage equations. Used as a historical formula reference, not as current eligibility guidance.
- U.S. Navy — Guide 4: Body Composition Assessment (February 2025, PDF) . Reference for the classic neck, abdomen, natural-waist and hip measurement sites. This calculator does not reproduce the current official Navy assessment.
- Potter AW et al. (2022). Circumference-Based Predictions of Body Fat Revisited . Frontiers in Physiology, 13:868627. DOI: 10.3389/fphys.2022.868627. Research comparing circumference estimates with DXA and discussing limitations.
- American Council on Exercise — Anthropometric Measurements: When to Use this Assessment (2014) . Body-fat percentage category chart; used for the sex-specific reference bands, separately from the Navy estimation formula.
Calculations run in your browser. This calculator does not send your measurements to a server or save them in browser storage.