Water Intake Calculator

Estimate your daily water needs based on weight, activity, climate, and life stage. All calculations run locally in your browser.

Calculate Your Daily Water Goal

We use your weight, activity, climate, and life stage to estimate a practical hydration target.

What this tool can do

Estimate your daily water needs with a modern, science-based approach that adapts to your lifestyle and environment.

Why you need this tool

Hydration needs change with activity, weather, and life stage. A one-size-fits-all “8 glasses” rule often doesn’t fit. This calculator gives you a personalized target so you can stay hydrated without guessing.

Technical terms explained

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Technical FAQ

Why does weight matter most for hydration?

Body weight correlates with total body water and metabolic rate. The baseline formula (Weight kg × 0.033) is a widely accepted starting point for daily needs.

How much extra water do I really need when exercising?

We add 350ml for every 30 minutes of sweat-inducing activity. This aligns with general sports nutrition guidance for moderate-intensity exercise.

Does hot weather really increase my needs by 0.5L?

Yes. In hot/humid climates, sweat losses rise significantly. Adding ~0.5L is a conservative adjustment to prevent dehydration.

Do tea and coffee count toward my water goal?

Yes, they do count, but they have a mild diuretic effect. We still recommend most intake from plain water for optimal hydration.

Is my data sent to any server?

No. All calculations happen in Vanilla JavaScript on your device. No external APIs are used for calculation.