Water Intake Calculator.
Stay hydrated.
Find out exactly how much water your body needs daily — personalised for your weight, activity level, and climate. Free, no signup.
Hydration is one piece of the puzzle. Calculate your calorie deficit and macros to reach your goal weight.
Try the Calorie Deficit Calculator →How much water should you drink per day?
Water needs vary significantly based on body size, activity level, and climate. A widely-used baseline is 35ml of water per kilogram of body weight. A 70kg person would need roughly 2.45 litres at rest — more if they exercise or live in a hot climate.
The old "8 glasses a day" rule is a rough approximation that doesn't account for individual differences. A personalised calculation gives a much more accurate target.
Why hydration matters for weight loss
Water plays a direct role in fat metabolism. Studies show that drinking water before meals reduces calorie intake, and staying well-hydrated supports the kidneys in processing the byproducts of fat breakdown. Mild dehydration also suppresses energy levels, making exercise harder and recovery slower.
If you're in a calorie deficit, aim to drink water consistently throughout the day — not just when thirsty. Thirst is a late signal that dehydration has already begun.
Signs you're not drinking enough water
The easiest indicator is urine colour. Pale yellow means you're well hydrated. Dark yellow or amber means you need more water. Other signs of underhydration include headaches, fatigue, difficulty concentrating, dry skin, and constipation.
Does coffee count as water intake?
Caffeinated drinks like coffee and tea have a mild diuretic effect but still contribute positively to overall hydration. Research shows that moderate coffee consumption (3–4 cups/day) does not cause dehydration in regular drinkers. However, water and herbal teas remain the most efficient hydration sources.
Frequently asked questions
Can you drink too much water?
Yes, though it's rare. Drinking excessive amounts of water in a short period can dilute sodium levels in the blood (hyponatremia). This is mostly a risk during endurance sports. For most people, following a personalised daily target spread across the day is completely safe.
Should I drink more water when exercising?
Yes. Add roughly 500ml for every hour of moderate exercise, and more in hot conditions. Your calculator result already accounts for your general activity level — but on specific intense training days, drink extra.
Does food count towards water intake?
Yes — fruits, vegetables, and soups contribute 20–30% of most people's daily water intake. High-water foods like cucumber, watermelon, and lettuce are particularly good. This calculator focuses on drinking water; food sources are a bonus on top.