Water Intake Calculator

What does this Water Intake Calculator do?

This calculator estimates a baseline daily water target using a common weight-based guideline, then adds an allowance for exercise since sweating increases fluid needs.

The formula

Base intake (ml) = weight (kg) × 35, plus an additional allowance based on daily exercise duration (roughly 350 ml extra per 30 minutes of exercise).

Step-by-step example

For someone weighing 68 kg who exercises 30 minutes a day: base = 68 × 35 = 2,380 ml, plus 350 ml for exercise = 2,730 ml total, or roughly 2.7 liters — about 11 glasses of 250 ml each.

Tips & common mistakes

• This is a general guideline, not a medical prescription — actual needs vary with climate, diet (especially sodium intake), pregnancy, and certain health conditions.
• Water from food (fruits, vegetables, soups) also contributes to hydration — this calculator estimates fluid from drinking specifically.
• Thirst is a reasonably reliable signal for most healthy adults; use this number as a rough target rather than a strict daily quota.

Signs you might not be drinking enough

Common everyday indicators of mild dehydration include dark yellow urine, headaches, fatigue, and dry mouth — though thirst itself is usually a reliable enough signal for most healthy adults to simply drink when they feel thirsty rather than closely tracking a precise daily number.

Factors that increase water needs beyond this estimate

Hot or humid weather, high altitude, fever or illness, pregnancy and breastfeeding, and high-sodium diets all increase fluid needs beyond a baseline weight-based estimate — this calculator provides a reasonable starting point for an average day, not a precise figure for every circumstance.

Frequently asked questions