Health Calculator Methodology
Last updated: February 2025
Overview
Our health calculators use medically-established formulas endorsed by leading health organizations including the World Health Organization (WHO), National Institutes of Health (NIH), and peer-reviewed medical literature. We prioritize scientific accuracy while making health metrics accessible to everyone.
Core Formulas Used
Body Mass Index (BMI)
BMI = weight (kg) / height (m)²The WHO-standard formula for assessing body weight relative to height. BMI categories: Underweight (<18.5), Normal (18.5-24.9), Overweight (25-29.9), Obese (≥30).
Basal Metabolic Rate (BMR)
Mifflin-St Jeor: BMR = (10 × weight) + (6.25 × height) - (5 × age) + sWhere s = +5 for males, -161 for females. This is the most accurate BMR formula according to the American Dietetic Association, preferred over the older Harris-Benedict equation.
Daily Water Intake
Base: 30-35 mL per kg body weightBased on Institute of Medicine guidelines, adjusted for activity level, climate, and individual factors. General recommendation: 2.7L/day for women, 3.7L/day for men.
Body Fat Percentage (Navy Method)
Men: 86.010×log10(waist-neck) - 70.041×log10(height) + 36.76The U.S. Navy circumference method, which correlates well with underwater weighing and DEXA scans while requiring only a tape measure.
Data Sources & Verification
- BMI categories from World Health Organization (WHO)
- BMR formulas validated against peer-reviewed studies in the Journal of the American Dietetic Association
- Hydration guidelines from National Academies of Sciences
- Calorie estimates based on NHS and USDA guidelines
Update Frequency
Health calculators are reviewed bi-annually against current medical literature. When major health organizations update their guidelines (such as WHO BMI categories or dietary recommendations), we update our calculators within 30 days.
Medical Disclaimer
Important: Our health calculators are for informational and educational purposes only. They are not a substitute for professional medical advice, diagnosis, or treatment. Always consult your physician or qualified health provider with questions about a medical condition. Never disregard professional medical advice or delay seeking it based on calculator results.