Water Intake Calculator
Free water intake calculator. Estimate daily water needs from body weight, exercise, and climate in liters, cups, and bottles. No signup.
What is a water intake calculator?
A water intake calculator estimates how much water you need per day from your body weight, exercise, and climate. It turns the vague “drink more water” advice into a target in liters, cups, and bottles.
How this calculator works
- Enter your body weight in kg or lb.
- A baseline of about 33 ml per kg is applied.
- Exercise adds roughly 350–700 ml depending on intensity and duration.
- Hot and humid climates add extra for sweat loss.
How to use the result
- Space the total across the day rather than chugging — your body absorbs steady intake better.
- Add a glass before, during, and after exercise on top of the baseline.
- Check urine colour: pale yellow is the practical “hydrated enough” signal.
- In hot weather or hard training, the number is a floor — drink to thirst beyond it.
How much water should I drink a day?
A widely used rule is 30–35 ml per kilogram of body weight — about 2.5–3 liters for a 70 kg adult — rising with exercise and heat. That’s roughly 8–13 cups, or 5–6 standard water bottles. Needs vary with activity, climate, and diet, so treat it as a starting target.
Common mistakes
- Chasing one universal number. A 50 kg office worker and a 90 kg labourer have very different needs.
- Ignoring food. About 20% of daily water comes from food — the target is total, not just what you drink.
- Drinking without thirst in training. Sweat losses can outpace what thirst tells you in heavy sessions.
Hydration underpins training and recovery — the TDEE calculator estimates the calories you burn while exercising, and the heart rate zones calculator helps you keep effort in the right band for your goals.