BMI & Body Fat Calculator
Not sure if the scale weight you’re seeing is mostly fat, muscle, or just normal fluctuation? This calculator combines BMI with a US Navy tape-measure body fat estimate to give you a clearer body composition snapshot— including lean mass, fat mass, and a simple goal-weight reference based on your height.
Your Measurements
Your Body Composition
BMI (Body Mass Index)
25.8
OverweightBody Fat %
7.1%
FitnessIdeal Body Weight
70lbs
Based on BMI 22Body Fat Mass
13lbs
Total fat weightLean Body Mass
167lbs
Muscle and bone weightWeight to Goal
110lbs
to loseBMI Categories (kg/m²)
Underweight
< 18.5
Normal
18.5-24.9
Overweight
25.0-29.9
Obese
>= 30.0
Body Fat Percentage Categories
Based on age and gender standards:
Male Categories
- Essential Fat: 2-5%
- Athletes: 6-13%
- Fitness: 14-17%
- Average: 18-24%
- Obese: 25%+
Measurement Tips
- Neck: Just below larynx
- Waist: At navel level
- Use flexible measuring tape
- Measure in same spot each time
Related Tools
Explore these additional calculators to optimize your health and fitness:
Understanding BMI and Body Fat Percentage
What This Body Composition Snapshot Includes
This page combines two different lenses on your body weight: BMI (height vs scale weight) and a US Navy tape-measure estimate (neck/waist, plus hip for females). The goal is to help you answer “is my weight mostly fat or mostly lean mass?” with a few simple inputs.
- BMI + category as a quick height/weight flag
- Body fat % from the Navy method (tape measurements)
- Fat mass and lean mass estimates in pounds
- Ideal-weight reference (height-based) and weight-to-goal context
For formulas, assumptions, and measurement notes used across calculators, see: Calculator Methodology.
How the Formulas Work
BMI Formula
BMI is calculated using a simple formula based on height and weight:
BMI = (weight in pounds / (height in inches)²) × 703This formula gives you a number that helps classify your weight status. While BMI is useful for population-level assessments, it doesn't distinguish between muscle and fat, so athletes or very muscular individuals may have a high BMI despite being healthy.
Body Fat Percentage Formula (US Navy Method)
This calculator uses the US Navy formula, which is more accurate than BMI alone because it accounts for body composition:
For Males:
BF% = 495 / (1.0324 - 0.19077 × log??(waist - neck) + 0.15456 × log??(height)) - 450
For Females:
BF% = 495 / (1.29579 - 0.35004 × log??(waist + hip - neck) + 0.22100 × log??(height)) - 450The Navy formula uses circumference measurements because fat distribution differs between body regions. Typical accuracy is within 3-4% of actual body fat when measured correctly.
Example Calculations
Example 1: Male, 180 lbs, 5'10"
Measurements:
- Height: 5'10" (70 inches)
- Weight: 180 lbs
- Neck: 15.5 inches
- Waist: 33 inches
Results:
- BMI = (180 / (70²)) × 703 = 25.8 (Overweight)
- Body Fat % = 18.5% (Average)
- Body Fat Mass = 33.3 lbs
- Lean Body Mass = 146.7 lbs
- Ideal Body Weight = 171 lbs
Example 2: Female, 150 lbs, 5'5"
Measurements:
- Height: 5'5" (65 inches)
- Weight: 150 lbs
- Neck: 13 inches
- Waist: 28 inches
- Hip: 36 inches
Results:
- BMI = (150 / (65²)) × 703 = 24.9 (Normal Weight)
- Body Fat % = 22.1% (Fitness)
- Body Fat Mass = 33.2 lbs
- Lean Body Mass = 116.8 lbs
- Ideal Body Weight = 148 lbs
How to Use The BMI & Body Fat Calculator
Step 1: Choose the body-fat formula path (male vs female)
Pick Male or Female first. On this page that decision changes two things immediately: the US Navy body fat equation used behind the scenes and whether you’ll need to enter a hip measurement.
Step 2: Enter height and scale weight to calculate BMI and “ideal weight”
Add your height and weight. This drives the BMI number and the height-based “ideal body weight” reference. (Age is included in the form, but the core calculations on this page are built from the measurements below.)
Step 3: Take tape measurements that the Navy method actually uses
Enter neck and waist circumference—then add hip only if you selected Female. Small measurement differences matter here, so be consistent.
Quick tape checklist:
- Neck: just below the larynx; tape level, not angled.
- Waist: at navel level, relaxed posture, normal breath.
- Hip (female): widest point of hips/glutes; tape stays horizontal.
- Use the same tape, same spots, same time of day when re-checking.
Step 4: Use the outputs to answer “what is my weight made of?”
Read the results as a composition snapshot:
- BMI: a height/weight category (can be misleading for muscular builds).
- Body fat %: the tape-based estimate you can track over time.
- Lean mass and fat mass: how much of your weight is estimated “not fat” vs fat.
- Weight to goal: how far your current weight is from the height-based reference used here.
Common Questions
Q: Is BMI alone enough to assess health?
No, BMI has limitations. It doesn't distinguish between muscle and fat, so athletes or very muscular people may have a high BMI despite being healthy. Using both BMI and body fat percentage provides a more complete picture of your body composition.
Q: How accurate is the Navy body fat formula?
The Navy formula is typically accurate within 3-4% of actual body fat percentage when measurements are taken correctly. For more precise measurements, consider professional methods like DEXA scans or hydrostatic weighing. However, for tracking progress over time, this calculator is highly consistent.
Q: What if my ideal weight seems too low?
The ideal weight is calculated based on a BMI of 22, which is in the middle of the normal range. Your personal ideal weight may vary based on muscle mass, bone structure, and individual factors. If you have significant muscle mass, a higher weight may be ideal for you. Consult with a healthcare provider for a personalized target.
Q: Should I measure myself multiple times?
Yes, it's a good idea to measure in the same location each time and take the average of multiple measurements. This helps account for minor variations in measurement technique. Measure yourself in the morning for consistency, and allow at least 2-4 weeks between measurements to see meaningful changes.
Q: What's the difference between body fat mass and lean body mass?
Body fat mass is the weight of all fat tissue. Lean body mass includes everything else: muscle, bone, organs, water, and connective tissue. Your total weight = body fat mass + lean body mass. When losing weight, the goal is usually to lose body fat while preserving or building lean body mass (through exercise and adequate protein).
Tips for Improving Your Body Composition
If You Want to Reduce Body Fat:
- Create a calorie deficit (eat less than you burn)
- Eat adequate protein to preserve muscle
- Do both cardio and strength training
- Get sufficient sleep (7-9 hours)
- Stay hydrated throughout the day
- Track progress weekly (weight can fluctuate daily)
If You Want to Build Muscle:
- Eat slightly above your calorie maintenance
- Consume adequate protein (0.8-1.0g per lb of body weight)
- Do resistance training consistently
- Allow time for recovery between workouts
- Prioritize whole, nutrient-dense foods
- Measure progress by strength gains and how clothes fit
Quick Reference
BMI Categories:
- Underweight < 18.5
- Normal 18.5-24.9
- Overweight 25.0-29.9
- Obese ? 30.0
Body Fat % (Males):
- Athletes 6-13%
- Fitness 14-17%
- Average 18-24%
- Obese 25%+
Body Fat % (Females):
- Athletes 14-20%
- Fitness 21-24%
- Average 25-31%
- Obese 32%+
Key Formulas
BMI Formula:
(Weight lbs / Height in²) × 703
Body Composition:
- Body Fat Mass = Weight × (BF% / 100)
- Lean Mass = Weight - Body Fat Mass
- Ideal Weight = Height² × 22 × 0.704882
Related Information
This calculator uses the US Navy body fat formula, which is one of the most accurate field methods for estimating body fat percentage.
For more accurate body fat measurement, consider professional methods like:
- • DEXA scanning
- • Hydrostatic weighing
- • Bioelectrical impedance analysis
- • Bod Pod scanning