Daily Water Intake Calculator
Find out how much water you should drink based on your body weight and activity
Daily Target
2.45 L
2450 ml per day
That's About
9.8
glasses (250ml each)
Hydration Tips
- Spread intake throughout the day — drink a glass every 1–2 hours rather than all at once
- Don't wait until you're thirsty — thirst is a late signal of dehydration
- Check your urine color — pale yellow = hydrated, dark yellow/amber = drink more
- Water-rich foods count too — fruits, vegetables, and soups contribute ~20% of daily intake
- Adjust for caffeine & alcohol — they have a mild diuretic effect; add 1 extra glass per caffeinated or alcoholic drink
The 35ml per kg guideline is the European Food Safety Authority (EFSA) recommended adequate intake for adults. Individual needs vary based on metabolism, diet, and activity level.
The Science of Hydration
Brain Function
Even mild dehydration (1–2% of body weight) can impair cognitive function, concentration, and short-term memory. The brain is ~75% water.
Physical Performance
Dehydration of just 2% body mass can reduce athletic performance by 10–20%. Proper hydration maintains blood volume and regulates body temperature.
Digestion & Kidneys
Water is essential for nutrient absorption, waste elimination, and kidney function. Chronic low intake is linked to kidney stones and UTIs.
📊 Hydration Guidelines By Source
| Organization | Men | Women | Per kg Formula |
|---|---|---|---|
| EFSA (Europe) | 2.5 L | 2.0 L | 35 ml/kg |
| IOM (USA) | 3.7 L | 2.7 L | ~30–40 ml/kg |
| WHO | 2.5–3.0 L | 2.0–2.5 L | 30–35 ml/kg |
This calculator uses the EFSA guideline of 35 ml/kg, which includes water from all sources (drinks + food).
💡 Signs You're Not Drinking Enough
- Dark urine — your kidneys are concentrating urine to conserve water
- Dry mouth & lips — reduced saliva production is an early dehydration sign
- Headaches — even mild dehydration can trigger tension headaches
- Fatigue — blood volume drops, making your heart work harder to deliver oxygen
- Dizziness — reduced blood pressure from low fluid volume
- Constipation — the colon absorbs more water when dehydrated, hardening stool
⚠️ Important: Individual hydration needs vary based on metabolism, diet, activity level, climate, and health conditions. Pregnant or breastfeeding women need additional fluids. Consult a healthcare provider for personalized advice, especially if you have kidney or heart conditions that require fluid restrictions.