Water Intake Calculator
Body-weight estimate with an exercise adjustment
A practical daily fluid target is about 35 ml per kg of body weight, plus roughly 12 ml per minute of exercise (≈ 700 ml per hour). For a 70 kg person doing 45 minutes of training that's about 2.45 + 0.54 ≈ 3.0 litres of total fluid, including water-rich food and other drinks. Enter your details below. These are general guidelines — drink to thirst and adjust for heat, altitude and sweat rate.
General hydration guidance, not medical advice. Needs vary with climate and health.
The formula
baseline (ml) = body weight (kg) × 35
exercise (ml) = exercise minutes × 12
total (ml) = baseline + exercise
litres = total ÷ 1000Heavy training days raise both your fluid and your energy needs — check the calories-burned calculator and set daily calories with the TDEE calculator.
Frequently asked questions
How much water should I drink per day?
A common rule of thumb is about 30–35 ml of fluid per kilogram of body weight per day, plus extra for exercise — roughly 350–700 ml per hour of activity. For a 70 kg person that's around 2.1–2.5 litres baseline. Food and other drinks also count toward total fluid.
What does this calculator's formula assume?
It uses about 35 ml per kg of body weight as a baseline and adds roughly 12 ml per minute of exercise (about 700 ml per hour). These are general guidelines, not precise medical requirements, and they include fluid from all beverages.
Does coffee or tea count toward water intake?
Yes. Despite the myth, moderate caffeinated drinks are mildly diuretic at most and still contribute net fluid. Water-rich foods like fruit, vegetables and soup also count toward your daily total.
Can you drink too much water?
Yes — drinking far more than you lose, especially during very long endurance events, can dilute blood sodium (hyponatraemia), which is dangerous. Drink to thirst, replace electrolytes during long efforts, and don't force large volumes well beyond these estimates.