Water Intake Calculator
Calculate your daily recommended water intake based on body weight, activity level, and climate. See how much water you should drink per day to stay hydrated.
Part of our Health Calculators collection.
Water Intake Calculator
Free online calculator
Results update automatically as you type
How to Use This Calculator
- 1
Enter your body weight.
- 2
Select your activity level.
- 3
Select your climate.
- 4
See your recommended daily water intake in cups, ounces, and litres.
Daily Water Intake Formula
Base intake = Body weight (lbs) × 0.5 oz = daily ounces Convert: ounces / 8 = cups | ounces / 33.814 = litres Activity adjustments: Moderately active: +12 oz (1.5 cups) Very active: +24 oz (3 cups) Athlete: +40 oz (5 cups) Climate adjustments: Hot: +16 oz | Very hot: +32 oz
Example Calculation
Example: 160 lbs, moderately active, temperate
Inputs
weightLbs: 160activityLevel: moderateclimate: temperate
Result
~92 oz/day (11.5 cups / 2.7 litres)
160 × 0.5 = 80 oz base + 12 oz for moderate activity = 92 oz per day.
Frequently Asked Questions
Does coffee and tea count towards water intake?
Yes — caffeinated drinks do contribute to hydration, contrary to the old myth. However, limit caffeine intake and prioritise plain water for optimal hydration.
Are the '8 glasses a day' rules accurate?
The 8×8 rule (8 glasses of 8 oz = 64 oz/day) is a rough guideline. Individual needs vary significantly based on weight, activity, and climate. This calculator gives a personalised estimate.