How much water should I drink in a day?

A common rule of thumb is around 30–40 mL of water per kilogram of body weight per day for healthy adults, but your exact needs depend on age, sex, activity level, climate, and whether you are pregnant or breastfeeding. This calculator uses a weight-based formula plus adjustments for these factors to estimate a personalized range.

Do coffee, tea, and other drinks count toward daily water intake?

Yes. Most beverages, including coffee and tea, contribute to your total fluid intake. However, very sugary drinks and heavy alcohol are not ideal sources of hydration. The calculator estimates total water from all sources, not just plain water, so many people can meet part of their needs through food and other drinks.

Should I follow this calculator if I have a medical condition?

No. This tool is for general education and for healthy adults. People with kidney disease, heart failure, liver disease, endocrine disorders, or on diuretics often need individualized fluid prescriptions. Always follow the advice of your doctor or dietitian instead of any generic calculator.

How accurate is a water intake calculator?

Any water intake calculator can only provide an estimate based on population averages. Real needs vary day to day with exercise, temperature, humidity, illness, and diet. Use the result as a starting point and adjust based on thirst, urine color, and how you feel, or seek personalized advice from a healthcare professional.

Daily Water Intake Calculator

Q: Is it possible to drink too much water?

Yes. Drinking extreme amounts of water in a short time can dilute blood sodium levels and lead to hyponatremia, which can be dangerous. This is rare in healthy adults who drink according to thirst and reasonable guidelines. If you have kidney, heart, or endocrine conditions, you should follow fluid limits set by your clinician rather than any online calculator.

Estimate how much water you should drink per day based on your weight, age, activity level, climate, pregnancy, and breastfeeding status.

Water intake calculator

Units

Metric (kg, cm, mL) US / Imperial (lb, ft/in, fl oz)

Weight

Use your current body weight. For children or medical conditions, ask a clinician for personalized advice.

Age

Sex (biological)

Daily activity level

Higher activity increases your water needs due to sweat losses.

Typical climate

Pregnant?

Breastfeeding?

Extra exercise today (minutes)

We add about 350 mL (12 fl oz) per 30 minutes of moderate–vigorous exercise.

Preferred output

Metric (L, mL) US (fl oz, cups) Show both

Your recommended daily water intake

Estimated range

Breakdown

Baseline (weight-based):
Activity adjustment:
Climate adjustment:
Pregnancy/breastfeeding:
Extra exercise:

Suggested drinking schedule

Spread your intake across the day instead of drinking large amounts at once.

Time	Amount

Quick hydration self-check

Urine is pale yellow or straw-colored most of the day.
You rarely feel very thirsty.
You have no unexplained headaches, dizziness, or extreme fatigue.

If these are not true for you, you may need to adjust your intake or speak with a healthcare professional.

How this daily water intake calculator works

There is no single “perfect” amount of water that fits everyone. This calculator uses a weight-based formula plus evidence-informed adjustments for age, sex, activity level, climate, pregnancy, and breastfeeding to give you a realistic daily range.

1. Baseline water needs (weight-based)

For healthy adults, a common estimate is 30–40 mL of water per kilogram of body weight per day. We use:

Baseline low: \( 30 \text{ mL} \times \text{weight (kg)} \)

Baseline high: \( 40 \text{ mL} \times \text{weight (kg)} \)

If you enter your weight in pounds, we convert to kilograms first:

\( \text{weight (kg)} = \text{weight (lb)} \div 2.2046 \)

2. Activity adjustment

Exercise increases sweat losses. We add an activity factor plus an optional extra adjustment for today’s planned workout:

Sedentary: +0 mL
Lightly active: +0.2 L
Moderately active: +0.5 L
Very active: +0.8 L
Athlete / intense training: +1.0 L

On top of that, we add roughly 350 mL (12 fl oz) per 30 minutes of moderate–vigorous exercise you enter for today.

3. Climate adjustment

Hot and humid environments increase fluid loss through sweat:

Cool / mostly indoors: no extra adjustment
Temperate: +0.25 L
Hot / humid: +0.5 L

4. Pregnancy and breastfeeding

Pregnancy and breastfeeding increase fluid requirements. We add:

Pregnant: +0.3 L
Breastfeeding: +0.7 L

These values are approximate and based on typical guideline ranges. Always follow the specific advice of your obstetrician or midwife.

5. Final recommended range

We apply all adjustments to both the low and high ends of your baseline range:

Low end: baseline low + activity + climate + pregnancy/breastfeeding + exercise

High end: baseline high + activity + climate + pregnancy/breastfeeding + exercise

The result is shown in liters, milliliters, US fluid ounces, and 240 mL “cups” so you can choose the format that’s easiest to track.

What counts toward daily water intake?

Your body gets water from several sources:

Plain water (still or sparkling)
Other beverages such as coffee, tea, milk, and juice
Water-rich foods like fruits, vegetables, soups, and yogurt

This calculator estimates total water from all sources. Many people can meet 20–30% of their daily needs from food alone, especially if they eat plenty of fruits and vegetables.

Signs you may not be drinking enough

Use your result as a starting point, then pay attention to how you feel. Common signs of mild dehydration include:

Dark yellow, strong-smelling urine
Feeling very thirsty or dry mouth
Headaches or difficulty concentrating
Fatigue, dizziness, or lightheadedness
Constipation

Severe dehydration is a medical emergency and can cause confusion, rapid heartbeat, rapid breathing, and fainting. Seek urgent care if you suspect severe dehydration.

Can you drink too much water?

Yes. Drinking very large amounts of water in a short time can dilute your blood sodium level and lead to hyponatremia, which can be dangerous. This is rare in healthy adults who drink according to thirst and reasonable guidelines, but it is more likely if:

You have kidney, heart, or liver disease
You take diuretics or certain psychiatric medications
You drink excessive water during endurance events without electrolytes

If you have any chronic medical condition or are on fluid restrictions, follow your clinician’s instructions instead of this calculator.

Who should not rely on this calculator?

This tool is intended for generally healthy adults. It is not appropriate as a primary guide for:

People with kidney disease or on dialysis
People with heart failure or severe liver disease
People with endocrine disorders affecting fluid balance
Children, frail older adults, or people with complex medical needs

In these cases, water and total fluid intake should be personalized by a healthcare professional who knows your medical history and lab results.

Practical tips to meet your daily water goal

Keep a reusable bottle with you and refill it throughout the day.
Drink a glass of water with each meal and snack.
Increase fluids before, during, and after exercise.
Eat more water-rich foods (fruits, vegetables, soups).
Use the schedule above as a gentle reminder, not a rigid rule.

This calculator is for educational purposes only and does not provide medical advice. Always consult your doctor or a registered dietitian for personalized recommendations.