Water Intake Calculator
Weight, exercise and weather in — a daily fluid target and an hourly pace out. A starting number, not a rule; thirst and urine color still have the final say.
Daily fluid target
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Common questions
How much water should I drink a day?
A common starting point is 30–35 ml per kg of body weight in total fluids, plus extra for exercise and heat. The US National Academies set adequate total water intake (food and drink) at about 2.7 L for women and 3.7 L for men; roughly 80% of that usually comes from drinks.
Do coffee and tea count toward water intake?
Yes. All drinks count, including coffee and tea — the mild diuretic effect of caffeine is small at normal intakes. Food, especially fruit and vegetables, supplies the rest.
Can you drink too much water?
Yes. Very large amounts in a short time, especially during long endurance events, can dilute blood sodium (hyponatremia). Spread intake across the day and let thirst guide you.
Method & sources
Baseline is 35 ml per kg body weight (top of the commonly cited 30–35 ml/kg adult band), rounded to 50 ml. Exercise adds 350–750 ml; hot conditions add 500 ml. Kidney or heart conditions, and medications like diuretics, change the answer entirely — follow your clinician's limit if you have one.
- National Academies — DRIs for water, potassium, sodium, chloride and sulfate (2005)
- EFSA — Scientific opinion on dietary reference values for water (2010)
On a GLP-1 medication? GLP-1 water calculator · Caffeine timing: caffeine cutoff calculator · sodium & potassium checker