Water Intake Calculator

Find out exactly how much water you should drink daily based on your body weight and activity level.

Use this free water intake calculator to find your personalized daily hydration goal. Enter your weight and activity level to get an instant recommendation in liters, ounces, and cups.

Your Details

Body Weight
kg
kglbs

Activity Level
Sedentary / Moderately Active / Active / Very Active

Climate
Temperate / Hot / Humid

Daily Water Intake

2.8
L / day
95
oz / day
11.8
cups / day
11
glasses / day

Hydration Tip
Drink water before, during, and after any exercise session. Carry a reusable bottle to stay on track.

Why Hydration Matters

How much water should I drink per day?

The commonly cited "8 glasses a day" guideline is a rough approximation. A more accurate method is to base your intake on body weight: roughly 33ml per kilogram of body weight. For a 70kg adult that is about 2.3 liters, but activity level and climate can push that figure significantly higher. This calculator applies those adjustments automatically.

Does exercise affect how much water I need?

Yes, significantly. During exercise you lose water through sweat and respiration. A moderate workout can add 500ml or more to your needs, while an intense session or endurance sport can require 1–2 extra liters. Always drink before you feel thirsty — thirst is a late signal of dehydration. This calculator boosts your target by 20–60% depending on your chosen activity level.

Can I count coffee and tea toward my water intake?

Partially. Coffee and tea do contribute to overall fluid intake, but caffeine has a mild diuretic effect that offsets some of the benefit. A good rule of thumb is to count caffeinated drinks at about 50–75% of their volume toward your daily target, and for every cup of coffee drink an extra half cup of plain water to compensate.

Does the climate affect my hydration needs?

Hot or humid weather increases sweat rate even at rest, raising your baseline requirement by 500–1000ml per day. High altitude also increases fluid loss through faster breathing. Selecting "Hot / Humid" in the calculator adds 500ml to your daily total to reflect this. On particularly hot days or after outdoor activity in the heat, consider drinking even more.

How to calculate daily water intake

Enter weight, activity level, and climate to estimate daily water needs in liters or ounces.

  1. Enter your body weight
    Water needs scale with body size. Enter weight in kilograms or pounds.

  2. Pick your activity level
    Add extra fluid if you exercise, sweat heavily, or live in a hot climate.

  3. Read your daily water target
    The calculator returns daily water in liters and ounces, plus a glasses-per-day breakdown.