Water intake calculator — daily hydration range
Estimate a practical daily drinking range from weight, exercise and heat, with glasses, hourly pace and transparent adjustments.
Estimate a daily drinking range
Use a practical range instead of a falsely exact target. These solved examples are editable and reset every input.
A planning estimate for healthy adults, not a medical prescription.
Even pacing across 16 waking hours
How the estimate works
The transparent planning heuristic uses 30 ml/kg, 350 ml per 30 minutes of exercise and 10% of the base in hot conditions. The result shows a ±10% range rather than false precision.
Total water is not plain water
Official reference intakes include water from food and every beverage. This editor instead estimates a practical drinking range, so the numbers must not be compared as if they measured the same thing.
When needs change
Heat, prolonged activity, fever, vomiting and diarrhea can change needs substantially. Electrolytes may matter during hours of sweating.
Important limits
Do not use this estimate with kidney or heart disease, a prescribed fluid restriction, pregnancy, breastfeeding, childhood or acute illness; clinical advice takes priority.
Private by design
Your weight and activity stay in this tab. They are never added to the URL, browser storage or analytics. Old shared links containing these fields are cleaned without restoring them.
Evidence context
The National Academies explains that adequate intake is not an exact individual requirement and that activity and heat increase needs. The CDC explains the role of water and other beverages.
Frequently asked questions
Do coffee and tea count?
Beverages and water-rich foods contribute to total intake. Sugar, alcohol and high caffeine intake need separate consideration.
Does everyone need exactly two litres?
No. Body size, diet, activity, climate and health differ. Use the range only as a planning starting point and follow thirst and clinical advice.
Why does the exercise example add 700 ml?
The editor adds 350 ml per 30 minutes: 60 minutes × 350 ml ÷ 30 minutes = 700 ml. Individual sweat loss can differ considerably.
Plan energy and nutrition separately with the calorie calculator.
