BodPod Body Composition Calculator

About Whole-Body Air-Displacement Plethysmography

Whole-Body Air-Displacement Plethysmography is a method for assessing body fat and lean mass, commonly using the BodPod machine. The method is similar to underwater (hydrostatic) weighing, but uses air instead of water.

Purpose: using air displacement technology for measuring and tracking body fat and lean mass.

Equipment required: BodPod by Life Measurements Instruments, Concord, CA.

Pre-test: Explain the test procedures to the subject. Perform screening of health risks and obtain informed consent. Prepare forms and record basic information such as age, height, body weight, gender, test conditions. Check and calibrate the equipment. See more details of pre-test procedures.

Procedure: The Bod Pod system measures body composition by determining body volume and body weight. The subject should not have exercised for the previous two hours, as they must be fully rested and hydration status and increases in muscle temperature can adversely affect the results. Body weight is measured using scales. Body volume is measured by first measuring the volume of the chamber while empty. Then the volume of the subject chamber is measured with the subject inside. By subtraction, the volume of the subject is determined. Once those body volume and weight are determined, body density can be computed and inserted into an equation to provide percent fat measurements.

body composition measurement using the bodpod

Method: Body volume is determined by monitoring changes in pressure within a closed chamber. These pressure changes are achieved by oscillating a speaker mounted between the front testing chamber and a rear reference chamber, which causes complementary pressure changes in each chamber. The pressure changes are very small and are not noticed by the individual being tested.

How to Use the BodPod Body Composition Calculator

Our calculator provides an estimate of what your body composition results would be using BodPod methodology. Follow these steps:

1. Select Your Units: Choose between metric (kg, cm) or imperial (lbs, inches) using the toggle switch.
2. Enter Your Measurements: Input your body weight, height, age, and gender. All fields are required for accurate calculation.
3. Calculate: Click the "Calculate Body Composition" button to see your estimated results.
4. Review Results: Your body fat percentage, fat mass, lean mass, and body density will be displayed along with athletic classification.
5. Interpret Categories: Compare your results to sport-specific standards to understand your body composition in athletic context.

Understanding Your Body Composition Results

Body composition assessment goes beyond simple weight measurement to determine how much of your body weight is fat mass versus lean mass (muscle, bone, organs, and water). The BodPod and our calculator use body density to estimate these components.

Body Fat Percentage Standards for Athletes

Athletic body fat percentages vary significantly by sport, position, and performance level:

Lean Mass Considerations

Lean body mass includes all non-fat tissue: skeletal muscle, organs, bone, and body water. For athletes, maximizing lean mass while maintaining optimal fat levels is crucial for performance. Research by Robert Wood, MSc Sports Science, indicates that lean mass development should be sport-specific—powerlifters benefit from maximal muscle mass, while distance runners optimize power-to-weight ratios with moderate lean mass.

The Science Behind BodPod Calculations

Air Displacement Plethysmography Methodology

The BodPod uses Poisson's Law to measure body volume by detecting pressure changes when a subject enters a sealed chamber. The system calculates:

1. Body Volume: Determined by measuring chamber pressure with and without the subject
2. Body Density: Calculated as mass (weight) divided by volume
3. Body Composition: Body density converted to fat percentage using the Siri equation

The Siri Equation

Body Fat % = (495 / Body Density) - 450

Developed by William Siri in 1961, this equation is based on the two-compartment model of body composition. The formula assumes fat tissue has a density of 0.9 g/cm³ and fat-free tissue has a density of 1.1 g/cm³, values determined through cadaver analysis.

Calculation Example

For a 180-pound (81.6 kg) male athlete, 70 inches tall, age 25:

• Step 1: Estimated body density = 1.065 g/cm³
• Step 2: Apply Siri equation: (495 / 1.065) - 450 = 14.8%
• Step 3: Fat mass = 81.6 kg × 0.148 = 12.1 kg
• Step 4: Lean mass = 81.6 kg - 12.1 kg = 69.5 kg

Result interpretation: At 14.8% body fat, this athlete falls in the "Elite Athlete" category, typical for competitive team sport athletes and optimal for most athletic performance goals.

BodPod Applications in Different Sports

Body composition requirements vary dramatically across athletic disciplines. Understanding sport-specific standards helps athletes optimize their body composition for peak performance.

Endurance Sports

Marathon Running, Cycling, Triathlon

• Optimal Range: Males 5-12%, Females 12-20%
• Elite Standards: Professional marathon runners typically maintain 6-8% (males) or 14-17% (females)
• Performance Impact: Each 1% reduction in body fat improves power-to-weight ratio by approximately 0.5-1%, directly enhancing endurance performance
• Monitoring: BodPod testing every 4-6 weeks during training helps prevent excessive fat loss that could impair recovery

Power and Strength Sports

Weightlifting, Powerlifting, Track & Field Throws

• Optimal Range: Males 8-20%, Females 15-25%
• Strategy: Moderate body fat acceptable as additional mass aids force production
• Weight Class Considerations: Athletes often target upper end of their weight class to maximize lean mass
• Off-season vs. Competition: Body fat may increase 3-5% during off-season training phases

Team Sports

Basketball, Soccer, Football, Hockey

• Position Variability: Guards/backs 10-15%, forwards 12-18%, linemen 15-25%
• Seasonal Changes: Pre-season typically 2-4% lower than post-season
• Performance Balance: Must balance speed, power, and endurance requirements
• Professional Examples: NBA players average 6-12% body fat, NFL running backs 6-10%, linemen 15-25%

Combat Sports

Wrestling, MMA, Boxing

• Weight Class Management: 8-15% body fat typical at competition weight
• Cutting Strategy: Athletes often maintain 5-10% above competition weight between fights
• Performance Optimization: Maximizing lean mass while staying within weight class limits
• Safety Monitoring: Regular BodPod testing ensures safe weight cutting practices

Advantages and Limitations of BodPod Testing

Advantages

• High Accuracy: ±1-2.7% error range, comparable to hydrostatic weighing considered the gold standard
• Fast Testing: Complete assessment in 10 minutes versus 30+ minutes for underwater weighing
• No Water Immersion: Eliminates discomfort and difficulty of underwater weighing
• Special Populations: Suitable for children, elderly, obese individuals, and those with physical limitations
• Minimal Subject Compliance: Simply sitting still versus complete underwater submersion
• Reproducibility: Excellent test-retest reliability (r = 0.99) for longitudinal tracking
• No Residual Lung Volume Measurement: Predicted values used, eliminating this technical challenge from hydrostatic weighing

Limitations

• Cost: BodPod units cost $30,000-$40,000, limiting availability to research institutions and elite training facilities
• Access: Few facilities offer BodPod testing; may require university or research center access
• Testing Costs: Individual tests typically cost $40-$75 when available
• Hydration Sensitivity: Results affected by hydration status; requires standardized pre-test conditions
• Clothing Requirements: Minimal, tight-fitting clothing and swim cap required for accuracy
• Movement Artifacts: Subject must remain completely still; talking or laughing invalidates test
• Population-Specific Accuracy: Some research suggests accuracy varies in very lean or very muscular athletes

Comparison to Other Methods

Optimizing Body Composition for Athletic Performance

Training Strategies Based on Body Composition Goals

If Body Fat Above Optimal Range:

• Implement moderate caloric deficit (300-500 calories daily) while maintaining protein intake at 1.6-2.2 g/kg body weight
• Increase resistance training frequency to preserve lean mass during fat loss
• Incorporate high-intensity interval training (HIIT) 2-3 times weekly for metabolic enhancement
• Monitor rate of fat loss: Target 0.5-1% body fat reduction monthly to preserve muscle mass
• Expected timeline: 8-16 weeks to achieve 3-5% body fat reduction for most athletes

If Body Fat Within Optimal Range:

• Maintain current training program and nutrition strategy
• Focus on performance metrics rather than composition changes
• Monitor for seasonal fluctuations (2-3% variation normal)
• Retest body composition every 8-12 weeks to track stability

If Body Fat Below Optimal Range:

• Evaluate energy availability: Low body fat may indicate insufficient caloric intake
• Assess for signs of overtraining or inadequate recovery
• Consider gradual increase in caloric intake (200-300 calories daily)
• Monitor for performance decrements, mood changes, or illness frequency
• Consult sports nutritionist or sports medicine physician for very low levels

Nutrition Strategies for Body Composition

Research by sports nutrition experts indicates that macronutrient distribution significantly impacts body composition changes:

• Protein: 1.6-2.2 g/kg body weight daily preserves lean mass during fat loss
• Carbohydrates: 3-7 g/kg for moderate training, 6-10 g/kg for high-volume endurance training
• Fats: Minimum 20-25% of calories for hormonal health, especially in female athletes
• Timing: Protein intake within 2 hours post-training optimizes muscle protein synthesis

Seasonal Periodization

Athletic body composition should vary throughout the training year:

• Off-Season (Building Phase): Body fat may increase 2-4% while building strength and lean mass
• Pre-Season (Preparation): Gradual reduction to optimal competition levels over 8-12 weeks
• In-Season (Competition): Maintain body composition with minimal fluctuation
• Post-Season (Recovery): Allow 1-2% increase while recovering from competition demands

Similar Tests

• Underwater (hydrostatic) weighing

Related Pages

• Other body composition tests
• About measuring body composition
• Videos of Anthropometric Tests
• Skinfold caliper store