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Water Calculator
Hydration is the dullest and most underrated performance factor there is: in longer endurance efforts, a deficit of more than two percent of your body weight noticeably costs performance. Calculate here how much you need today.
Conditions
Fluid needs today
3.5
litersabout 14 glasses of 250 ml
Where it comes from
Distribution over the day
Based on 33 ml per kilogram, plus 400 ml per half hour of training. For coffee and tea we add a small margin: with habituation, caffeine has hardly any diuretic effect, and those cups largely count as fluid themselves. If your urine is light in color, you are doing well — and if you eat a lot of soup, fruit, and vegetables, you already get part of this fluid from your meals.
Why exactly these factors?
Your fluid needs depend on your body weight as a baseline, plus extra fluid for sweat loss during training, warm weather, and the mild diuretic effect of caffeine.
How much water do I need at minimum?
As a rule of thumb, roughly 30 to 35 ml per kilo of body weight per day is the baseline, without training. In warm weather or during intense training, that quickly goes up.
Do coffee or tea count toward my fluid intake?
Largely yes — the mild diuretic effect of caffeine is small at moderate consumption. With a lot of caffeine per day, this calculator does account for it by recommending a small extra amount of water.
What are signs of too little fluid during exercise?
Thirst, dark urine, headache and tiring faster are often named as signals. In endurance efforts, performance drops noticeably from a fluid deficit of 2% of body weight or more; for strength there is no clear threshold. While exercising, the advice is to drink to thirst.
Can I also drink too much water?
Yes, although it is rare with normal daily intake. Extremely large amounts in a short time can disrupt sodium balance. For most people this is not a practical risk as long as you drink spread out over the day.