Water Intake Calculator

A water intake calculator estimates how much water you should drink daily based on your body weight and activity level. Proper hydration is essential for nearly every bodily function — from regulating temperature and transporting nutrients to supporting brain function and joint health.

This calculator uses a weight-based formula that accounts for your individual needs. A larger person needs more water than a smaller person, and physical activity increases water requirements through sweat and respiration. The calculator adjusts your baseline intake with an activity multiplier to give you a personalized recommendation.

Results are shown in liters, standard glasses (250ml each), and fluid ounces so you can track your intake however you prefer. Remember that roughly 20% of your daily water comes from food, so these recommendations include all sources of hydration.

1. Choose your unit system — Imperial (lbs) or Metric (kg).
2. Enter your weight — Your current body weight.
3. Select your activity level — From sedentary to very active.
4. View your recommendation — See daily water intake in liters, glasses, and fluid ounces.

Base Intake: Weight (kg) × 0.033 = liters per day

Activity Adjustment: Base × Activity Multiplier

Multipliers: Sedentary (1.0×), Light (1.12×), Moderate (1.25×), Active (1.5×), Very Active (1.75×)

Example: 70 kg, moderate activity → 70 × 0.033 × 1.25 = 2.9 L/day