How much water should I drink?

Q: How much water should I drink?

Drink to thirst, plus around 500 ml per hour of hard training; pale-yellow urine is the practical check.

Drink to thirst, plus around 500 ml17 fl oz per hour of hard training; pale-yellow urine is the practical check.

Evidence Moderate Reviewed 24 Aug 2026 Sources 2

The eight-glasses rule has no basis in evidence. Losing more than about 2% of bodyweight in fluid does measurably reduce endurance performance, which is what the per-hour figure is there to prevent.

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Sources 2

Sawka, M.N. et al. (2007). American College of Sports Medicine position stand: exercise and fluid replacement. Med Sci Sports Exerc 39(2). Recommends drinking to thirst for most athletes; individualised plans for heavy sweaters.
Institute of Medicine (2005). Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. National Academies Press. About 20% of daily water intake comes from food.