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Water Intake Calculator
A daily water target based on your bodyweight and activity level. The calculation is 35 ml per kg of bodyweight if you're sedentary, rising to 38, 40 and 45 ml per kg as training volume increases — so a 70 kg moderately active person lands at about 2.8 litres.
Treat it as a starting point, not a quota. Food contributes roughly 20% of total water intake, and thirst plus pale-yellow urine remain the most practical day-to-day guides.
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Why Hydration Matters for Fat Loss and Performance
Water is involved in virtually every physiological process in the body. For fat loss and fitness, hydration affects metabolic rate (even mild dehydration reduces metabolism by 3–5%), exercise performance (a 2% body weight water deficit reduces strength and endurance by up to 20%), digestion and nutrient absorption, hunger signaling (thirst is often mistaken for hunger), and liver function (the primary fat-burning organ requires adequate hydration).
Many people misinterpret thirst as hunger, leading to unnecessary snacking. Drinking a glass of water 20–30 minutes before meals consistently reduces calorie intake in studies. Adequate hydration also improves skin elasticity, cognitive function, and detoxification — particularly important during calorie restriction when the body is mobilizing stored fat and toxins.
Simple Hydration Habits That Work
- ✓Drink 500ml immediately after waking up — replenishes overnight fluid loss
- ✓Carry a 1L water bottle and refill it twice throughout the day
- ✓Drink 400–500ml 30 minutes before each workout
- ✓Include hydrating foods: cucumber (96% water), watermelon (92%), strawberries (91%)
- ✓Set hourly phone reminders if you struggle to remember to drink
- ✓Check urine color — pale yellow means well-hydrated, dark yellow means drink more
Frequently Asked Questions
How much water should I drink per day?
General guidelines: 35–45ml of water per kg of bodyweight, depending on activity level. A 70kg moderately active person needs approximately 2.5–3 liters per day. The old '8 glasses a day' rule is a rough approximation — your actual needs vary with bodyweight, exercise intensity, climate, and diet composition.
Does coffee or tea count toward daily water intake?
Yes — caffeinated beverages do contribute to hydration, despite the common myth that they are dehydrating. Studies show that moderate caffeine consumption (up to 5 cups/day) does not cause net fluid loss. However, water remains the optimal hydration source as it contains no calories, caffeine, or additives.
What are signs of dehydration?
Early signs (1–2% body weight water loss): thirst, dark yellow urine, reduced concentration, mild headache. Moderate (3–5% loss): significant fatigue, dizziness, reduced exercise performance, dry mouth. Severe (>5% loss): cramping, nausea, rapid heartbeat, confusion. Urine color is the easiest daily indicator — aim for pale yellow.
Should I drink more water when exercising?
Yes — significantly more. During exercise, add 500–750ml per hour of moderate exercise, and up to 1–1.5L per hour for intense training in hot conditions. Starting exercise well-hydrated and drinking throughout (not just after) prevents performance decline. Electrolytes matter for sessions over 60–90 minutes.
Can you drink too much water?
Yes — hyponatremia (water intoxication) occurs when excessive water intake dilutes sodium levels in the blood. This is rare in everyday life and typically only occurs in endurance athletes drinking plain water for hours without electrolytes. For most people, up to 1L per hour is safe. If you are extremely thirsty despite drinking normally, consult a doctor as this can indicate diabetes or other conditions.
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Browse Free RecipesMethod: 35–45 ml per kg of bodyweight by activity level — a practical heuristic, not an official reference value. See full methodology and limitations. Estimates for general education, not medical advice.