Water Intake Calculator
By Santaji GadepatilinUpdated October 27, 2026
How to use this calculator
Enter your body weight and how many minutes you exercise on a typical day. The estimate is shown in litres (or US gallons).
The formula used
Water (L) ≈ 0.033 × weight (kg) + 0.35 × (exercise minutes ÷ 30)
Worked example
A 70 kg adult who exercises 30 minutes a day:
- Base = 0.033 × 70 = 2.31 L
- Exercise = 0.35 L
- Total ≈ 2.66 L per day
Drink more when…
- it is hot or humid
- you are at high altitude
- you have a fever, vomiting or diarrhoea
- you are pregnant or breastfeeding (follow medical advice)
A simple check
Pale yellow urine usually means you are well hydrated. Dark yellow urine and thirst are signs to drink more.
This is a general estimate. Individual needs vary.
Frequently asked questions
How much water should I drink a day?
A common guideline is about 30–35 ml per kg of body weight, plus roughly 350 ml for every 30 minutes of exercise. For a 70 kg adult that is about 2.3 litres, plus extra for activity.
Does food and other drinks count?
Yes. Around 20% of daily water usually comes from food, and tea, coffee and milk also count towards your intake.
Can I drink too much water?
Yes, very large amounts in a short time can be dangerous. People with kidney or heart conditions should follow their doctor's advice.