How much water should I drink a day?

General adequate-intake guidance is about 3.7 liters of total water daily for men and 2.7 liters for women — including roughly 20% that comes from food. Body weight, activity, and climate move your personal target up or down.

Does coffee or tea count toward my water intake?

Yes. Despite caffeine's mild diuretic effect, caffeinated drinks still provide a net hydration benefit at normal consumption levels and count toward daily totals.

How much extra water do I need when exercising?

Plan on roughly 0.5-1 liter per hour of moderate exercise, more in heat. For precision, weigh yourself before and after: drink about 16-24 oz (500-700 ml) for every pound lost during the session.

What are the signs I'm not drinking enough?

Dark yellow urine, thirst, headache, fatigue, and reduced concentration are the common early signals. Pale straw-colored urine is the usual target for adequate hydration.

Can you drink too much water?

Yes — excessive intake in a short period can dilute blood sodium (hyponatremia), a real risk in endurance events. Drink to thirst, spread intake through the day, and include electrolytes during very long efforts.

Water Intake Calculator

Calculate your daily water intake based on weight, age, activity level, and climate. Get personalized hydration targets

Personal Information

Units

Weight (kg)

Age

Gender

Pregnancy Status

Current Daily Intake (ml)

Lifestyle Factors

Activity Level

Climate

Altitude

Caffeine (cups/day)

Alcohol (drinks/day)

Workout (minutes)

Daily Water Recommendation

3.6L

Personalized daily target

Base Needs

2.5L

Without adjustments

Current Deficit

1.6L

Need more water

Hourly Target

226ml

Spread throughout waking hours

Adjustment Factors

Physical Activity

Moderate activity level

+500ml

Caffeine Intake

2 cups of caffeinated beverages daily

+300ml

Extended Exercise

60 minutes of exercise

+360ml

Water from Food Sources

Cucumber:96%

Lettuce:95%

Watermelon:92%

Cantaloupe:90%

About 20% of daily fluid intake comes from food

How it works

Your daily water need scales with body size and activity. A common rule of thumb is about 35 ml of water per kilogram of body weight (or, in imperial terms, roughly half your body weight in pounds, in ounces). The calculator starts there and adjusts up for exercise and hot weather.

Baseline daily water

Metric:  ml ≈ 35 × kg        Imperial:  oz ≈ ½ × lb        + ~350–700 ml per hour of exercise

kg / lb: body weight
exercise: extra fluid to replace sweat losses

Worked example

Body weight = 70 kg
Light activity

Baseline = 35 × 70 = 2,450 ml

About 2.5 litres (~84 oz) a day — more on workout or hot days.

Good to know

About 20% of daily water comes from food (fruit, vegetables, soups), so you don't need to drink the entire target.
Thirst and urine colour are good real-time guides — pale yellow means well-hydrated.
These are healthy-adult estimates; certain medical conditions require a doctor-set fluid target instead.