The Formula (European Food Safety Authority):

text 
Base Requirement: 30-35ml per kg of body weight
Activity Add: 500ml per 30 minutes of exercise
Climate Add: 500ml for hot/humid conditions

Example Calculation:

For 70kg (154lb) person, moderate activity:
  1. Base: 70kg × 35ml = 2,450ml
  2. Activity: 60min exercise = +1,000ml
  3. Total: 3,450ml (≈ 12 cups)

Timing Optimization (Based on Chronobiology):

Morning (7-9 AM): 500ml cold water

Why: Body temperature rises naturally, cold water requires energy to warm = +24% metabolic rate for 90 minutes

Pre-Meals (30 minutes before): 250ml per meal

Study: University of Birmingham found this reduces calorie intake by 13%

During Exercise: 150-200ml every 15 minutes

Science: 2% dehydration reduces performance by 10-20%

Evening (2 hours before bed): Final 250ml

Why: Supports overnight detoxification without disrupting sleep

Urine Color Scale (Armstrong LE, 1994):

  • Pale yellow (1-3): Optimal hydration
  • Dark yellow (4-6): Mild dehydration
  • Brown/orange (7-8): Medical attention needed
Citations:
  1. EFSA Panel on Dietetic Products (2010). EFSA Journal, 8(3), 1459.
  2. Boschmann, M., et al. (2003). Journal of Clinical Endocrinology & Metabolism, 88(12), 6015-6019.
  3. Corney, R. A., et al. (2016). European Journal of Nutrition, 55(2), 617-624.