Water Intake by Activity Calculator

About this calculator

Daily water needs are commonly estimated as a baseline amount tied to body weight — a widely used rule of thumb is roughly half an ounce to one ounce of water per pound of body weight (or about 30 to 35 ml per kilogram) — and that baseline has to rise with physical activity to replace fluid lost through sweat.

This calculator adds a per-minute allowance for exercise on top of the weight-based baseline, since sweat rate and exercise duration both drive additional fluid loss beyond resting needs, giving a hydration target tuned to how much you actually move rather than a single one-size-fits-all number.