This calculator uses the Galpin equation to calculate your recommended water intake during your workout.

1- Too little water: Dehydration
"Dehydration occurs when more water and fluids leave the body than enter it. Even low levels of dehydration can cause headaches, lethargy, and constipation. The human body is roughly 75 percent water. Without this water, it cannot survive." ─ Medical News Today

2- Water & Exercise
"Above meeting your baseline hydration requirements (80 oz/10 hrs of waking), other factors such as exercise, sweating, excess heat, dry environments and caffeine intake affect your hydration requirements. When exercising, follow the Galpin Equation as a guideline for the amount of additional fluid you should consume (again, on average — no need to be neurotically obsessed with consuming exact amounts at exact times during exercise, unless you prefer to). ─ HubermanLab

3- Too much water: Overhydration
"Most people, especially those who exercise in hot weather, are concerned about not drinking enough water. However, it’s possible to have too much water in your body. This can cause water toxicity. This is when your body’s water is more thanTrusted Source your kidneys can excrete. It can lead to a dangerous electrolyte imbalance." ─ Healthline