04 · Water Intake
Water Calculator
There's no single "eight glasses a day" rule that fits everyone — needs scale with body size, how hard you're training, and how hot it is. This gives you a starting daily target, in millilitres or ounces.
Daily target
—ml
Enter your weight to see a starting hydration target for today.
How it's calculated
We start from a baseline of about 35 ml per kilogram of body weight, then add roughly 350–500 ml for exercise depending on duration, and another 10% on top for hot or humid conditions. Coffee, tea, and food also contribute to daily fluid intake, and this figure doesn't replace listening to thirst or checking urine colour as a simpler day-to-day signal. People with kidney, heart, or other conditions that affect fluid balance should follow their clinician's guidance instead.