Water Intake Calculator
Daily hydration target by weight and activity.
About this tool
This calculator uses the widely cited 33 ml-per-kg starting point, adds about 350 ml per 30 minutes of exercise, and 500 ml extra in hot climates. Total fluid includes water, tea, coffee, and food (about 20% of intake).
The headline message: your urine colour is the best practical guide. Pale straw means you're well hydrated; dark amber means drink more.
Frequently asked questions
Does coffee count?
Yes. The diuretic effect of moderate caffeine is small and net hydration is positive.
Can I drink too much water?
Yes — water intoxication (hyponatraemia) is rare but possible with very high intake during endurance events. Drink to thirst rather than forcing a target.
What if I have heart failure or kidney disease?
Follow your clinician's specific fluid guidance — generic targets may be too high for you.
⚕️ Educational only — not a substitute for professional medical advice, diagnosis, or treatment. In an emergency call your local emergency services.