Scientific Standards

    Our Calculator Methodology

    Every calculator on FitnessProGuide uses a formula published in peer-reviewed research or established by a recognized health authority. Below is the complete reference list for all 37+ tools - the formula used, its origin, and the academic citation.

    CalculatorFormula UsedSource
    BMI CalculatorBody Mass Index (kg/m²)World Health Organization (WHO), 2000
    BMR CalculatorMifflin-St Jeor Equation (primary); Harris-Benedict (alternative)Mifflin et al., Am J Clin Nutr, 1990; Harris & Benedict, 1919
    TDEE CalculatorMifflin-St Jeor × Activity MultiplierMifflin et al., 1990; McArdle WD et al., Exercise Physiology, 2015
    Calorie CalculatorMifflin-St Jeor + Activity FactorSame as TDEE
    Macro CalculatorISSN position stand protein targets; ACSM carbohydrate guidelinesStokes T et al., Nutrients, 2018; ACSM, AND, DC Joint Position Statement, 2016
    Protein Calculator1.6–2.2 g/kg bodyweightMorton RW et al., Br J Sports Med, 2018
    Body Fat CalculatorUS Navy Method; BMI-based methodHodgdon & Beckett, 1984; Deurenberg P et al., 1991
    Calorie Deficit CalculatorEnergy balance: 7,700 kcal ≈ 1 kg fatHall KD et al., Lancet, 2011
    Ideal Weight CalculatorDevine formula (primary); Robinson, Miller, Hamwi formulasDevine BJ, 1974; Robinson JD et al., 1983
    One Rep Max CalculatorEpley formula (primary); Brzycki formulaEpley B, 1985; Brzycki M, 1993
    Heart Rate CalculatorTanaka formula for max HR; Karvonen method for zonesTanaka H et al., JACC, 2001; Karvonen MJ et al., 1957
    VO2 Max CalculatorACSM metabolic equationsACSM Guidelines for Exercise Testing and Prescription, 10th Ed
    Running Pace CalculatorPace = Distance ÷ TimeStandard mathematical relationship
    Water Intake CalculatorNational Academies: 3.7 L/day men, 2.7 L/day women total waterNational Academies of Sciences, 2004
    Sleep Calculator90-minute sleep cycle modelCarskadon MA & Dement WC, Principles of Sleep Medicine, 2011
    Army Body Fat CalculatorUS Army Regulation 600-9 circumference methodAR 600-9, 2019
    Lean Body Mass CalculatorBoer formula (primary); James formula; Hume formulaBoer P, 1984; James WPT, 1976; Hume R, 1966
    Wilks Score CalculatorWilks formula (2017 update)Wilks RC, IPF Technical Rules, 2017 revision
    Body Recomposition CalculatorSimultaneous deficit/surplus modelBarakat CI et al., Strength Cond J, 2020
    Pregnancy Weight Gain CalculatorIOM (ACOG) guidelines by pre-pregnancy BMIACOG Practice Bulletin, 2013
    Intermittent Fasting Calculator16:8, 18:6, 20:4 fasting window modelsLongo VD & Panda S, Cell Metabolism, 2016
    Creatine CalculatorLoading: 0.3 g/kg/day × 5–7 days; Maintenance: 3–5 g/dayKreider RB et al., JISSN, 2017
    BMI Body Fat % CalculatorDeurenberg equationDeurenberg P et al., Br J Nutr, 1991
    Bench / Squat / Deadlift 1RMEpley, Brzycki (same as 1RM calculator)As above
    Steps to CaloriesMET-based energy expenditure estimationAinsworth BE et al., Compendium of Physical Activities, 2011

    A Note on Formula Accuracy

    All calculators produce estimates, not clinical measurements. Population-level formulas cannot account for individual variation in genetics, muscle fiber composition, hormonal status, hydration, or medical conditions. Results should be treated as starting points and adjusted based on real-world outcomes over 2–4 weeks.

    For clinical measurements, consult a registered dietitian, certified trainer, or licensed healthcare provider.

    Suggest a Formula Update

    If you believe a more recently validated formula should replace one of the above, please contact us with the peer-reviewed citation. We review all formula update suggestions and will update the tool if the evidence supports it.

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