What is a water intake calculator?
A water intake calculator turns your body weight and daily activity into a rough target for how much to drink. Bigger bodies hold more water and lose more through normal metabolism, so they need more to top up. Exercise adds to that through sweat, which is why active days call for extra.
The number you get is a sensible starting point for a typical day. Heat, altitude, caffeine, illness, and pregnancy all shift it, so treat the result as a guide and let thirst and urine colour fine-tune the rest.
How it is calculated
The calculator uses a weight-based baseline and then adds for exercise:
- Baseline: 35 ml of water for every kilogram you weigh.
- Exercise add-on: 500 ml for every 30 minutes of activity.
So the full method is water (ml) = weight(kg) × 35 + (exercise minutes ÷ 30) × 500, then converted to litres and fluid ounces. Here is how that plays out for a few examples:
| Weight | Exercise | Daily water |
|---|---|---|
| 60 kg | none | 2.1 L |
| 70 kg | 30 min | 3.0 L |
| 90 kg | 60 min | 4.2 L |
Food counts too. Fruit, vegetables, soups, and other moist foods cover part of your fluid for the day, so you rarely need to drink every millilitre on top of meals.
Frequently asked questions
How much water should I drink a day?
A common starting point is about 35 ml of water per kilogram of body weight, then add roughly 500 ml for every 30 minutes of exercise. For a 70 kg person that works out to around 2.5 litres on a rest day. This is an estimate, so adjust for hot weather, illness, and how thirsty you feel.
Does drinking water help with weight loss?
Water has no calories, and drinking a glass before meals can help you feel full so you eat a little less. Replacing sugary drinks with water also cuts calories over the day. Water itself does not burn fat, so pair it with a calorie-aware diet and regular movement.
Should I drink more water on a GLP-1 medication?
People on GLP-1 medications often eat and drink less, which can make mild dehydration easier to slip into, and nausea can reduce fluid intake further. Sipping water through the day usually helps. These are general notes, not medical advice, so ask your prescriber what is right for you.
Plans and guides
Hydration is one piece. Here is where to put the rest of your plan to work.
Keep going: find your daily calorie needs with the TDEE calculator, or check your BMI.