Calculate the optimal daily hydration for yourself or your clients based on body weight, hours of physical activity, and climate conditions. An essential tool for optimizing performance and health.
It uses a base formula of 35 ml per kg of body weight, adjusted for physical activity (+500 ml per hour of exercise) and hot climate (+500 ml). These are general recommendations that may vary between individuals.
Check this if your client trains in summer, in a gym without air conditioning, or lives in a hot climate region.
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Daily water needs vary from person to person. Body weight, activity level, and climate are the three main factors that determine how much water you actually need. The widely used baseline of 35 ml per kg of body weight comes from European Food Safety Authority (EFSA) guidelines and serves as a solid starting point for healthy adults.
| Body weight | Sedentary | 1 h exercise/day | 2 h exercise/day |
|---|---|---|---|
| 60 kg (132 lb) | 2.1 L | 2.6 L | 3.1 L |
| 70 kg (154 lb) | 2.5 L | 3.0 L | 3.5 L |
| 80 kg (176 lb) | 2.8 L | 3.3 L | 3.8 L |
| 90 kg (198 lb) | 3.2 L | 3.7 L | 4.2 L |
These figures include all fluids — not just plain water. Coffee, tea, soups, and water-rich foods all contribute. That said, plain water remains the best default choice for hitting your daily target without adding extra calories.
When you exercise, your muscles generate heat. To cool down, your body sweats — and that sweat has to be replaced. A moderate one-hour workout can add 500 ml or more to your daily fluid needs. High-intensity sessions or training in hot conditions can push that figure significantly higher.
Research shows that a body water deficit of just 2% of body weight is enough to impair physical performance and cognitive function. This is why coaches and athletes take pre-session hydration seriously rather than waiting to feel thirsty.