Get your personalised daily water target based on weight, activity level, climate, and whether you're pregnant or breastfeeding.
There is no single universal answer — your ideal water intake depends on your body size, how active you are, the climate you live in, and whether you are pregnant or breastfeeding. The famous "8 glasses a day" rule is a rough average that does not account for individual variation.
The National Academies of Sciences recommends a total daily water intake of 3.7 litres (125 oz) for men and 2.7 litres (91 oz) for women — including water from all food and drinks, not just plain water. About 20% of water intake typically comes from food. A common starting formula is 35 ml per kilogram of body weight per day, adjusted upward for activity and heat.
Dark yellow urine (aim for pale straw), feeling thirsty, headaches, difficulty concentrating, and fatigue are the most common signs of mild dehydration. By the time you feel thirsty, you are already mildly dehydrated.
Yes. Despite the mild diuretic effect of caffeine, research shows that caffeinated beverages still contribute net fluid to the body. A cup of coffee or tea counts towards total daily fluid intake, though plain water remains the ideal choice.
A general guideline is an extra 400–600 ml (14–20 oz) for every 30–60 minutes of moderate exercise. In hot weather or during high-intensity activity, losses can be significantly higher. Weigh yourself before and after exercise — every 1 kg lost equals approximately 1 litre of fluid deficit.
Yes — overhydration (hyponatraemia) can occur when water intake greatly exceeds kidney excretion capacity, typically above 0.8–1 litre per hour sustained over several hours. This is rare outside of endurance sports. For most people, thirst is a reliable guide and the kidneys handle the rest.