How much water should you drink a day?
The short answer: around 2.7 liters a day for women and 3.7 for men, including water from food, which in practice means roughly 8 to 12 cups of fluids. But the honest answer is that your number changes daily with heat, humidity and how much you sweat.
Where the classic advice comes from
The famous 8 glasses rule is a simplification of total fluid intake guidelines, which include the water in food. Fruit, vegetables, soup and coffee all count toward the total, so the amount you need to drink as plain water is usually less than the headline number.
Thirst is a decent guide at rest, but it lags behind real losses during exercise and in hot weather. By the time you feel thirsty on a training day, you are often already behind.
What actually changes your need
Sweat is the big variable. An hour of hard training can cost anywhere from half a liter to two liters depending on intensity, temperature and humidity. Body size matters too: bigger bodies lose more.
Signs you are under target are simple: dark urine, headaches in the afternoon, and fatigue that lifts after a glass of water. Overdrinking plain water to extremes is rare but real, so the goal is matching intake to loss, not maximizing it.
A target that adapts, not a fixed rule
A fixed daily goal ignores the difference between a rest day in winter and a leg day in July. Your real need can easily swing by a liter or more between those two days.
Equil calculates a daily water goal from your base need, then adds what you actually lose: it reads the day's weather and humidity, estimates your sweat from your workouts, and raises the target in real time. You just drink to the number.
Stop tracking by hand
Equil reads your food, glucose, sleep and training, then adjusts your plan in real time. Not another logger, a coach.
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