Exercise changes the question.

Why we do not add a fixed amount per hour

Sweat losses vary with intensity, conditions and the person. The American College of Sports Medicine position stand discusses individualized fluid replacement. A single exercise multiplier cannot represent all those situations.

What recent research says about recovery

A systematic review by Borra and colleagues in Journal of Athletic Training (2025 issue) compared carbohydrate-electrolyte drinks with water after exercise-induced dehydration. Some outcomes favored these drinks, but evidence certainty was low or very low. The studies took place in laboratory settings, and the search ended in June 2022. This review concerns recovery after fluid loss, not a universal amount to drink during every workout.

Heat and age change the context

Kim and colleagues, Scientific Reports (2026), compared spring and summer measurements in 26 older Japanese adults. Average water turnover increased by 0.640 L per day in summer. The data were collected in 2012, and the study did not measure urinary indicators of hydration. That group average is not an extra drinking allowance for everyone. It helps explain why a daily reference needs context, especially for older adults in hot conditions.

Work in the heat is a different setting

For outdoor work, use the CDC/NIOSH workplace recommendations and your workplace heat-safety plan. Do not treat a daily bottle count as an hourly goal.

More is not always better

The 2015 exercise-associated hyponatremia consensus addresses the risks of excessive fluid intake during exercise. Its recommendations have a specific sporting context; adding electrolytes does not make unlimited drinking safe.

For long events, repeated heavy sweating or medical concerns, seek an individualized plan from a qualified professional. This site does not calculate that plan.

Evidence reviewed September 7, 2026. See our method and limits.