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Water Intake Calculator

Estimate your recommended daily water intake based on weight and activity.

Recommended Daily Intake

2.6L

≈ 89 fl oz · 11 cups

Related Guide

Water Intake Calculator: How Much Water Should You Really Drink?

Read Guide →

About This Tool

Free water intake calculator online — enter your body weight, activity level, and climate to estimate how much water you should drink per day, in both liters and ounces/cups. No sign-up, no upload, entirely browser-based. The often-cited "8 glasses a day" rule is a rough generalization that ignores body size and activity — this calculator instead scales water needs to your actual body weight, then adjusts upward for exercise (which increases fluid loss through sweat) and hot climates (which increase perspiration).

How to Use

  1. 1

    Enter your weight

    Input your body weight in kilograms or pounds.

  2. 2

    Select your activity level

    Choose sedentary, moderately active, or very active based on your typical exercise.

  3. 3

    Select your climate

    Choose temperate or hot/humid to adjust for extra fluid loss through sweat.

Frequently Asked Questions

Is "8 glasses a day" accurate for everyone?+
Not really — it's a simple rule of thumb that doesn't account for body size, activity level, or climate. A 200 lb active person in a hot climate needs considerably more water than a sedentary 120 lb person in a cool climate.
Does this include water from food?+
No, this estimates total fluid intake from drinking. Roughly 20% of daily water intake typically comes from food, so this figure is a reasonable target for what to drink, not necessarily on top of food-derived water.
Do I need more water on workout days?+
Yes — exercise increases fluid loss through sweat, so the calculator's "very active" setting adds extra recommended intake to account for this on top of baseline needs.

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