ZenFit Tools Sports Science and Gym Analytics

Gym-Tech Physiological Architecture · 2026 Edition

Elite Health, Nutrition & Biohacking Analytics

Educational sports science, nutrition, and metabolic calculators based on published formulas and references. Client-side calculations with transparent methodology.

Instant Client-Side Math

ACSM & ISSN Aligned

In-Browser Processing

Evidence-Based Analytics

Explore The 19 Elite Physiological Tools

Select any calculator below to open its dedicated analytics workstation, peer-reviewed formulas, and clinical guidelines.

Showing 19 of 19 Tools

5 min readCore Metric

TDEE & Daily Calorie Burn Calculator

Estimate your Total Daily Energy Expenditure (TDEE) and basal metabolic rate using published Mifflin-St Jeor and Katch-McArdle equations.

TDEE = BMR × Physical Activity Level (PAL)Calculate

6 min readNutrition Suite

Advanced Macronutrient & Macro Split Estimator

Estimate balanced protein, carbohydrate, and dietary fat ratios tailored to fat loss, muscle hypertrophy, or ketogenic protocols.

Caloric Budget = (Protein × 4 kcal) + (Carbohydrate × 4 kcal) + (Fats × 9 kcal)Calculate

4 min readAnthropometry

US Navy Body Fat Percentage Calculator

Empirical body circumference method adopted by the United States Department of Defense for estimated body composition assessment.

Logarithmic circumference regression modeling height, neck, waist, and hipsCalculate

5 min readPower & Strength

One-Rep Max (1RM) & Strength Standards Calculator

Calculate your maximum single-rep strength using 6 peer-reviewed formulas and view customized percentage-based training loads.

Brzycki, Epley, Lombardi, Mayhew, O'Conner, and Wathan empirical modelsCalculate

4 min readCardiovascular Suite

Target Heart Rate & Training Zones Calculator

Determine your 5 cardiovascular physiological training zones based on Tanaka age-predicted maximum and Karvonen Heart Rate Reserve.

Tanaka Max HR = 208 - (0.7 × Age) | Karvonen Target = Rest HR + [% × (Max HR - Rest HR)]Calculate

4 min readEndurance Science

Running Pace & Race Time Predictor

Convert split paces (min/km & min/mile) and predict 5K, 10K, Half, and Full Marathon times using Pete Riegel’s fatigue equation.

Riegel Fatigue Model: T2 = T1 × (D2 / D1)^1.06Calculate

5 min readCircadian Biology

Intermittent Fasting Window & Autophagy Timer

Plan daily feeding windows (16:8, 18:6, 20:4, OMAD) and explore general educational fasting milestones and metabolic adaptations.

Temporal feeding boundaries & cellular lysosomal autophagy progressionCalculate

3 min readElectrolyte Balance

Daily Water & Hydration Intake Calculator

Calculate volumetric fluid requirements based on body mass, exercise sweat rate, environmental climate, and electrolyte dynamics.

Fluid Requirement = (Body Mass × 35 ml/kg) + Exercise Sweat Loss + Climate AdjustmentCalculate

4 min readErgogenic Aids

Creatine Loading & Dosage Calculator

Calculate optimal creatine monohydrate loading vs steady saturation protocols and daily maintenance doses based on lean body mass.

Loading: 0.3 g/kg/day (divided 4×) for 5-7 days | Maintenance: 0.03-0.05 g/kg/dayCalculate

5 min readNatural Limit Benchmarks

Lean Body Mass (LBM) & FFMI Calculator

Calculate Fat-Free Mass Index (FFMI) and normalized FFMI to evaluate natural muscularity benchmarks based on Kouri et al. cohorts.

FFMI = LBM (kg) / Height (m)² | Normalized = FFMI + 6.1 × (1.8 - Height)Calculate

4 min readAnthropometry

Ideal Body Weight & Bone Frame Size Calculator

Compare Devine, Robinson, Miller, and Hamwi clinical equations with wrist circumference bone frame size calibrations.

Devine, Robinson, Miller, & Hamwi clinical formulas + r-value frame ratioCalculate

6 min readHypertrophy Models

Maximum Muscular Potential Estimator

Estimate your natural reference range for drug-free lean mass and maximum muscle girths using Casey Butt and Martin Berkhan models.

Casey Butt Skeletal Frame Model & Berkhan Leangains EquationCalculate

3 min readCardiometabolic Health

Waist-to-Height Ratio (WHtR) & Health Risk Calculator

Screen central adiposity and cardiometabolic risk using the Ashwell Shape Chart methodology. WHtR is a screening indicator associated with cardiometabolic risk.

WHtR = Waist Circumference / Height | Target: Keep your waist to less than half your heightCalculate

4 min readEnergy Expenditure

Calories Burned per Exercise Calculator

Calculate exercise energy expenditure for 35+ sports and strength activities using the Compendium of Physical Activities MET database.

Calories = (MET × 3.5 × Body Mass in kg / 200) × Duration in MinutesCalculate

4 min readSleep Timing

Sleep Cycle & Circadian Wake-Up Estimator

Explore bedtime and wake times using an approximate sleep-cycle model. Individual sleep cycles vary, so this result is educational and not a medical assessment.

Approximate 90-Minute Sleep Cycle Model + 14-Minute Average Sleep LatencyCalculate

5 min readClinical Comparison

Basal Metabolic Rate (BMR) Comparative Calculator

Side-by-side comparative analysis of Mifflin-St Jeor, Revised Harris-Benedict, Katch-McArdle, and Schofield WHO equations.

Comparative matrix across 4 clinical BMR prediction methodologiesCalculate

5 min readAnabolic Optimization

Protein Intake Timing & Distribution Calculator

Optimize Muscle Protein Synthesis (MPS) by calculating per-meal leucine thresholds, meal distribution frequency, and nocturnal micellar casein.

Per-Meal Dose = 0.40 - 0.55 g/kg | Leucine Threshold = 2.7 - 3.2g per bolusCalculate

7 min readBody Recomposition

Body Recomposition & Caloric Surplus/Deficit Planner

Plan concurrent adipose reduction and skeletal muscle hypertrophy with periodized caloric budgeting and high-protein partitioning.

Iso-caloric to Mild Deficit (-10% to 0%) + Protein at 2.2 - 2.6 g/kgCalculate

4 min readCardio Physiology

Heart Rate Reserve (HRR) & Cardio Intensity Zone Calculator

Calculate Karvonen Heart Rate Reserve zones factoring individual resting pulse for aerobic training guidance.

Target HR = Resting HR + [% Intensity × (Max HR - Resting HR)]Calculate

Specialized Category Hubs

Browse our curated physiological clusters designed around specific training, metabolic, and biometric goals.

5 Core Calculators

Metabolism & Diet

Evidence-based mathematical models for caloric expenditure, estimated thermogenesis, nutrient partitioning, and fasting physiology.

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5 Mathematical Models

Body Composition

Anthropometric formulas, logarithmic circumferences, lean mass tracking, and natural muscular thresholds.

Explore Hub Calculators

5 Athletic Tools

Cardio & Strength

Cardiopulmonary reserve metrics, fatigue kinetics, maximal strength standards, and metabolic equivalent expenditure.

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4 Longevity Tools

Biohacking & Recovery

Ultradian sleep architecture, cellular hydration dynamics, cellular ergogenic saturation, and chronobiology.

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Educational Sports Science & Published Research Standards

Formulas derived from published literature including ACSM, ISSN, DoD, and PubMed references

Every tool within ZenFit Tools is engineered from published sports science and nutritional literature. From Mifflin-St Jeor metabolic equations and Hodgdon-Beckett circumference methods to Casey Butt's muscular models and Tanaka heart rate formulas, calculations provide educational estimates based on published formulas and references rather than speculative gym-lore.

Read Full Methodology & Citations•Medical & Clinical Disclosures