HomeTools
Log InGet Started
  1. Home
  2. Tools
  3. BMI & Body Fat Calculator

BMI & Body Fat Calculator

Calculate your BMI and body fat percentage using the US Navy method

Calculator

Enter your measurements for accurate results

Weight Unit

Measurement Unit

Basic Information

Gender
lbs

Body Measurements

in
Measure around your neck just below the Adam's apple
in
Measure around your natural waistline (narrowest point)

Your results will appear here

Fill in your measurements and press Calculate.

Important Medical Disclaimer
These calculations are for informational purposes only and should not replace professional medical advice. Please consult with a healthcare provider for personalized health assessments and recommendations.
Fitspot app — Train by Recovery. Not by the Calendar.

About the US Navy Method

The US Navy method provides a more accurate estimation of body fat percentage compared to BMI alone, especially for individuals with higher muscle mass. It uses body circumference measurements to calculate body fat percentage using scientifically validated formulas developed for military fitness standards.

Note: This calculator uses the original US Navy formulas which were calibrated using measurements in inches. All measurements are converted to inches before applying the formula for maximum accuracy.

Measurement Tips

  • Take measurements in the morning for consistency
  • Use a flexible measuring tape, not a rigid ruler
  • Keep the tape snug but not tight - don't compress the skin
  • Measure over bare skin when possible for accuracy
  • Stand in a relaxed, natural position while measuring
  • Take measurements 2-3 times and use the average for best results
  • Ensure measurements are larger than neck: waist > neck (men), waist + hip > neck (women)

Understanding Your Results

BMI Categories:

  • Underweight: Less than 18.5
  • Normal: 18.5 - 24.9
  • Overweight: 25.0 - 29.9
  • Obese: 30.0 and above

Body Fat Standards:

Men:

  • Essential: 2-6%
  • Athletes: 6-14%
  • Fitness: 14-18%
  • Average: 18-25%
  • Above Avg: 25%+

Women:

  • Essential: 10-16%
  • Athletes: 16-20%
  • Fitness: 20-25%
  • Average: 25-32%
  • Above Avg: 32%+

Accuracy Note:

Body fat calculations are estimates. Factors like muscle mass, bone density, and body composition can affect accuracy. For precise measurements, consider DEXA scans or hydrostatic weighing.

The formulas behind this calculator

Body Mass Index (BMI)

BMI = weight (kg) ÷ height (m)². In imperial units, BMI = 703 × weight (lb) ÷ height (in)². A BMI of 18.5–24.9 is classed as normal weight, 25–29.9 as overweight and 30 or above as obese.

US Navy body-fat percentage

The US Navy circumference method estimates body fat from your measurements in inches (this calculator converts your units for you automatically):

  • 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

Frequently Asked Questions

For most people the US Navy circumference method lands within roughly 3-4% of lab-grade methods like DEXA, which is excellent for a tape-measure estimate. Accuracy depends on measuring consistently: same time of day, tape snug but not compressing the skin, and the exact landmarks described under each field. Very muscular or very lean physiques can read slightly high or low.

For adults, a BMI of 18.5-24.9 is classed as normal weight, 25-29.9 as overweight, and 30 or above as obese. BMI is a screening number, not a diagnosis — it only compares weight to height, so it can misclassify muscular people. That is exactly why this calculator also estimates body fat percentage alongside BMI.

The US Navy formula estimates body fat from the contrast between circumferences: the waist (plus hips for women) tracks where fat is stored, while the neck acts as a proxy for lean body structure. The bigger the gap between them relative to your height, the higher the estimated body fat percentage.

Yes. Muscle is denser than fat, so a muscular lifter can register as "overweight" by BMI while carrying low body fat. When your BMI and body fat percentage disagree, the body fat estimate is usually the more meaningful number for training decisions — and lab methods like DEXA are the gold standard.

Sources & references

  • •Hodgdon, J. A. & Beckett, M. B. (1984). Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, San Diego — the origin of the circumference ("US Navy") body-fat method used by this calculator.
  • •World Health Organization — BMI classification for adults: underweight below 18.5, normal 18.5–24.9, overweight 25–29.9, and obese 30 or above.
  • •U.S. Centers for Disease Control and Prevention (CDC) — About Adult BMI and its use as a screening (not diagnostic) measure.

Built by Fitspot, a recovery-based workout tracker that schedules each session when the muscle is actually recovered. Start training with Fitspot free.

Also try our One Rep Max Calculator
LoginGet Started
BMI & Body Fat CalculatorOne Rep Max Calculator
© 2026 Fitspot, All rights reserved
Terms of UsePrivacy Policy