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Water Intake Calculator — how much water to drink daily
This water intake calculator helps you estimate how much fluid to drink each day. The starting point is body weight — we use about 33 ml of water per kilogram. We then add fluids lost during physical activity and apply a correction for hot ambient conditions. Just enter your body weight, daily minutes of exercise and choose whether you are in moderate or hot conditions. The calculator instantly returns your requirement in litres, millilitres and convenient 250 ml glasses. Results are indicative. Actual needs depend on health, climate, diet and individual factors. With kidney or heart conditions, consult your doctor.
How the water intake calculator works
The calculator runs three steps: 1. Base requirement = body weight x 0.033 litres. 2. Activity addition = (minutes / 30) x 0.35 litres. 3. If the temperature is hot, the total is multiplied by 1.15. Litres are then converted to millilitres (x 1000) and to glasses (millilitres / 250, rounded). All values are indicative.
Example: 70 kg, 30 minutes of activity, moderate temperature
Base requirement: 70 kg x 0.033 = 2.31 litres. Activity: (30 / 30) x 0.35 = 0.35 litres. Total: 2.31 + 0.35 = 2.66 litres. Moderate temperature — no correction. Result: 2.66 litres = 2660 ml = about 11 glasses of 250 ml. In hot conditions the result would rise by 15%: 2.66 x 1.15 = about 3.06 litres.
Frequently asked questions
How much water should I drink daily?
Roughly 30-35 ml per kilogram of body weight. For 70 kg that is about 2.3-2.5 litres. The calculator adds fluids for activity and hot temperature.
How does the calculator estimate the requirement?
Body weight x 0.033 litres is the base. We add 0.35 litres per 30 minutes of exercise, and in hot weather multiply the total by 1.15.
Are these values accurate?
No, they are indicative. Actual needs depend on health, climate, diet, pregnancy and breastfeeding. It is a starting point, not a fixed norm.
Do coffee and tea count toward fluid balance?
Yes, moderate amounts count toward your daily fluid balance. Plain water remains the best source of hydration as it has no sugar or calories.
How can I tell I am dehydrated?
Signs include dark urine, thirst, dry mouth, headaches and fatigue. Light, straw-coloured urine usually indicates good hydration.
Can I drink too much water?
Yes, very large amounts in a short time can cause hyponatremia. For most people the risk is low when drinking according to thirst.
Why drink more in hot weather?
In high temperatures the body sweats more and loses water and electrolytes, so the calculator increases the requirement by 15%.
Should people with kidney or heart conditions use this result?
Not without consulting a doctor. With such conditions fluid intake is often strictly limited or individually adjusted.
Indicative result
Results are purely indicative and do not constitute medical advice. Actual fluid needs depend on health, climate, exercise intensity, diet, pregnancy and other factors. With kidney disease, heart conditions, hypertension or other chronic illnesses, consult a doctor before changing your fluid intake.
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