Your body is roughly 60% water, and you lose some through breathing, sweat and digestion every day. This calculator gives a practical daily target based on your weight, activity and climate.
How to use the Water Intake Calculator
- 1 Enter your body weight in kilograms.
- 2 Enter how many minutes you exercise on a typical day.
- 3 Pick your climate, then read your target in litres, ounces and glasses.
Formula
Base = weight (kg) × 0.033 L Active = +0.35 L for every 30 minutes of exercise Total = (Base + Active) × climate factor
Worked examples
Input: 70 kg, 30 min exercise, temperate
Result: ≈ 2.66 L/day
About 11 glasses of 250 ml
Does all of it have to be plain water?
No. Tea, coffee, milk and water-rich foods such as fruit, vegetables and soups all count towards hydration. Food typically provides around 20% of total water intake.
Signs you need more water
Dark yellow urine, thirst, headaches and fatigue can all indicate mild dehydration. Pale straw-coloured urine is a good everyday indicator that you are drinking enough. People with kidney or heart conditions may need to limit fluids — follow medical advice.
This calculator provides general estimates for healthy adults and is not medical advice. Consult a doctor or registered dietitian before making significant changes to your diet or exercise.
Frequently asked questions
Is 8 glasses a day right for everyone?
It is a reasonable rule of thumb, but needs vary with body size, activity, climate, pregnancy and health.
Can you drink too much water?
Yes. Drinking very large amounts in a short time can dilute blood sodium (hyponatremia). Spread intake through the day.
Does coffee dehydrate you?
Moderate coffee intake has a mild diuretic effect but still contributes net fluid overall.
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