Daily hydration target based on weight, activity, and climate.
A commonly used baseline is 0.5 oz of water per pound of body weight per day. Activity level and climate significantly affect this number — athletes exercising in hot weather may need double the baseline amount.
Signs of mild dehydration include fatigue, headache, and reduced exercise performance. Thirst is a reliable indicator for most people, but older adults and those exercising intensely should drink proactively. Coffee, tea, and food also contribute to daily fluid intake.