Water Intake Calculator
Health
Daily water intake calculator
Enter your body weight and choose a hydration guideline to estimate how much water you should drink each day.
Water Intake Calculator
Daily water (ml)
2,450 ml
Daily water (L)
2.45 L
Weight
70 kg
How calculations work
This tool multiplies body weight by a guideline value in millilitres per kilogram to estimate daily fluid needs. It is a simple, general heuristic used in public guidance (for example, 30–40 ml per kg). Calculations run locally; no external services are used.
How to interpret results
The output is a general daily target for average conditions. Individual needs vary with activity, climate, pregnancy, and health conditions. Treat this number as a guideline, not a prescription.
Disclaimer
What this calculator does
This calculator estimates your recommended daily fluid intake by multiplying your body weight by a hydration guideline expressed in millilitres per kilogram. It outputs a daily target in both millilitres and litres, giving you a personalised baseline that is more individualised than the generic "8 glasses a day" advice.
Who should use this calculator
Anyone wanting a personalised hydration guideline — fitness enthusiasts tracking fluid intake, people managing weight, outdoor workers in warm climates, or anyone starting a health improvement plan. It is a general-purpose tool and not a replacement for medical advice from a doctor or dietitian.
How this calculator works
Enter your body weight in kilograms and select a guideline value in ml/kg. Common guidelines range from 30 ml/kg (sedentary adults in temperate climates) to 40 ml/kg or higher (active individuals or warm environments). The formula is simple: Daily target (ml) = Weight (kg) × Guideline (ml/kg). All calculations run locally in your browser — no data is transmitted.
How to interpret your result
The output is a baseline daily target. Increase it on days with intense exercise, hot weather, or illness (fever, vomiting). Decrease slightly if you eat water-rich foods (fruits, soups, salads) that contribute to fluid intake. Aim to distribute consumption evenly throughout the day — sipping regularly is more effective than consuming large amounts at once.
Example
A 70 kg person using the 35 ml/kg guideline has a daily target of 70 × 35 = 2,450 ml (about 2.45 litres or roughly 10 cups). A lighter 55 kg person at the same guideline needs 55 × 35 = 1,925 ml (about 1.9 litres). Adjust the guideline slider to see how different activity levels change your target.
Limitations & disclaimer
This is an informational guideline based on general hydration research. It does not account for specific medical conditions (such as kidney disease or heart failure), medications that affect fluid balance, pregnancy, or breastfeeding. People with health conditions should consult a healthcare provider for personalised hydration recommendations.
Frequently asked questions
Does coffee or tea count toward daily water intake?
Moderate amounts of caffeinated beverages do contribute to total fluid intake. However, water remains the best choice because it has no calories, sugar, or additives. High caffeine intake (above 400 mg/day for most adults) may have a mild diuretic effect.
Should I drink more water when exercising?
Yes. The American College of Sports Medicine recommends drinking about 500 ml (17 oz) of fluid roughly two hours before exercise and replacing fluids lost through sweat during and after activity. Use a higher ml/kg guideline value if you exercise regularly.
Can I drink too much water?
Overhydration (hyponatremia) is rare but possible, especially during intense endurance exercise. It occurs when sodium levels drop dangerously low from excessive water intake. Spread your intake across the day rather than consuming large amounts at once.
Does climate affect how much water I need?
Hot or humid conditions increase sweat rates and therefore fluid needs. If you live in a warm climate or spend time outdoors in heat, increase your daily target by selecting a higher guideline value (e.g. 40 ml/kg instead of 30 ml/kg).
Is the "8 glasses a day" rule accurate?
The "8 × 8" rule (eight 8-oz glasses, about 1.9 litres) is easy to remember but not evidence-based for all individuals. Actual needs depend on body weight, activity level, climate, and diet. This calculator provides a weight-based estimate that is more personalised.