Body Composition Calculators

Estimate Total Daily Energy Expenditure and maintenance calories using Mifflin-St Jeor BMR, refined with Katch-McArdle when body fat is available. Activity multipliers range from sedentary (1.2) to competitive (1.9). TDEE is the foundation for calorie planning, fat loss, and lean bulk targets.

Calculate daily calorie targets for fat loss (cutting at 85% TDEE), lean bulk (108%), aggressive bulk (115%), or recomposition (98%). Conservative multipliers optimize fat mobilization while preserving muscle mass. A practical starting point for body composition strategy planning.

Estimate daily maintenance calories (TDEE at net energy balance) using Mifflin-St Jeor BMR with activity factor multipliers. The baseline for all calorie planning — confirmed when weight trend is stable under consistent intake. Foundation for fat loss and lean bulk targets.

Estimate a sustainable calorie deficit for fat loss. Applies a 15% deficit below TDEE to optimize fat mobilization while defending muscle tissue. Moderate deficit supports training quality, adherence, and long-term body composition progress.

Estimate a controlled calorie surplus for muscle gain. Lean bulk: 5-8% above TDEE. Aggressive bulk: 12-15% above TDEE. Choose a smaller surplus to limit unnecessary fat gain while maximizing muscle protein synthesis during lean bulking.

Calculate Basal Metabolic Rate (BMR), the calories burned at complete rest. Uses Mifflin-St Jeor by default; Katch-McArdle when body fat is available. BMR accounts for 60-70% of TDEE and serves as the resting baseline for all calorie planning.

Estimate daily protein intake for muscle protein synthesis, fat loss, and lean mass retention. Based on ISSN guidelines: 1.6-2.2 g/kg body weight adjusted by goal. Higher end (2.2 g/kg) recommended during calorie deficit to prevent muscle catabolism.

Determine daily protein, fat, and carb targets aligned with calorie goals. Sets protein first (1.9 g/kg), dietary fat at 28% of calories, then allocates remaining calories to carbohydrates. Practical macro planning for body composition diet adherence.

Estimate body fat percentage using the US Navy Circumference Method. Uses neck, waist, and hip measurements with sex-specific logarithmic formulas. Outputs body fat percentage, lean mass, and fat mass for body composition assessment and strategy selection.

Calculate Fat-Free Mass Index (FFMI) to quantify muscle mass relative to height. Uses raw FFMI with Kouri height normalization to correct tall-athlete skew. Provides body composition context beyond BMI for training and strategy planning.

Calculate Lean Body Mass (LBM) from body weight and body fat percentage. LBM = Weight × (1 - BF/100). Differentiates metabolic tissue from stored fat for body composition assessment, calorie targeting, and goal planning.

Calculate Body Mass Index (BMI) as a weight-to-height screening metric. Categorizes results into underweight, normal (18.5-24.9), overweight, and obese ranges. BMI is a population screening tool, not a body composition assessment.

Calculate Waist-to-Height Ratio (WHtR) as a central adiposity screening metric. A ratio of 0.50 or higher indicates increased cardiovascular risk. Often more predictive than BMI alone for health context and body composition planning.

Generate a comprehensive body composition snapshot integrating BMI, WHtR, lean mass, fat mass, and body fat percentage. A multi-dimensional assessment to inform training and nutrition strategy selection for fat loss or muscle gain.

Forecast timeline to reach target body weight using compounding metabolic decay rather than linear projection. Accounts for metabolic adaptation with conservative weekly rates: 0.75% for fat loss, 0.2-0.4% for muscle gain. Generates non-linear projection curves for realistic planning.

Display height-based reference weight range using healthy BMI parameters (18.5-24.9). Provides a flexible range accounting for skeletal frame variation — not a single prescriptive target. Context for body composition goal setting.

Calculate target body weight from current lean mass and desired body fat percentage. Formula: Target Weight = LBM / (1 - Target BF%). Assumes lean mass is held constant. Practical for setting body composition goals with your strategy.

Project realistic muscle gain using the Alan Aragon rate model. Beginners: 0.2% body weight per week. Intermediates: 0.1%. Advanced: 0.05%. Training age, program quality, and adherence strongly affect lean bulk outcomes and timelines.

Calculate calorie and protein targets for simultaneous fat loss and muscle gain. Near-maintenance calories (2% deficit) with higher protein emphasis (2.2 g/kg). Recomp progress is slower; judge results beyond scale weight using body composition trends.