How Much Water Should You Drink a Day?

You have probably heard that you should drink eight glasses of water a day, but the real answer to how much water should you drink a day depends on you. Your body size, activity level, the weather, and even what you eat all play a role. This guide explains the general guidelines from health experts, how to adjust them for exercise and heat, how to tell if you are drinking enough, and simple ways to stay hydrated without overthinking it.

Why Your Body Needs Water

Water makes up more than half of your body weight, and nearly every system depends on it. Your body uses water to:

• Regulate body temperature through sweat
• Carry nutrients and oxygen to your cells
• Cushion joints and protect your spinal cord
• Flush waste through urine and bowel movements
• Support digestion and help prevent constipation
• Keep your energy and concentration steady

You lose water constantly through breathing, sweating, and going to the bathroom. That water needs to be replaced every day through drinks and food.

How Much Water Should You Drink a Day? The General Guidelines

The U.S. National Academies of Sciences, Engineering, and Medicine set general adequate intake levels for healthy adults living in a temperate climate:

These numbers include all fluids, not just plain water. Coffee, tea, milk, soup, and juicy foods all count. On average, about 20 percent of daily fluid intake comes from food, especially fruits and vegetables like watermelon, cucumbers, oranges, lettuce, and strawberries.

That means the amount you need to actually drink is lower than the totals above. Mayo Clinic offers a helpful overview in its article on how much water you need each day.

For a personal estimate based on your weight and activity, try our calculator.

When You Need More: Exercise, Heat, and Other Factors

Your baseline needs go up in several situations. Plan ahead for these.

Exercise

Any activity that makes you sweat increases your fluid needs. For a typical workout, drink some water before you start, sip during exercise, and drink more afterward. If you work out for longer than an hour or sweat heavily, you also lose sodium and other electrolytes, so a sports drink or a salty snack can help.

A simple way to gauge your sweat losses is to weigh yourself before and after a workout. Any weight you lost is mostly water, and you can replace it gradually over the following hours. If you are just getting into running, our beginner's guide to starting a running routine includes more tips for training comfortably.

Hot or humid weather

Heat and humidity make you sweat more, even when you are not exercising. Drink regularly throughout the day and do not wait until you feel very thirsty. High altitude can also increase fluid needs.

Illness

Fever, vomiting, and diarrhea all cause fluid loss. Sip water often, and consider an oral rehydration solution if you cannot keep fluids down for long. Contact a doctor if symptoms are severe or last more than a day or two.

Pregnancy and breastfeeding

Pregnant and breastfeeding people need extra fluids. Talk to your doctor or midwife about what is right for you.

Signs of Dehydration

Thirst is your body's built-in alarm, but by the time you feel very thirsty, you may already be mildly dehydrated. Watch for these signs:

• Feeling thirsty or having a dry mouth
• Dark yellow urine or urinating less often than usual
• Headache or difficulty concentrating
• Fatigue or low energy
• Dizziness or lightheadedness, especially when standing up
• Dry skin or lips
• Muscle cramps during or after activity

The Urine Color Check

One of the easiest ways to monitor hydration is to glance at your urine. It is not perfect, but it is a useful everyday guide.

Some vitamins, especially B vitamins, can turn urine bright yellow, and foods like beets can tint it pink or red. Keep that in mind before you worry.

Can You Drink Too Much Water?

Yes, although it is rare for most people. Drinking a very large amount of water in a short time can lower the sodium level in your blood. This condition, called hyponatremia, can cause nausea, headache, confusion, and in serious cases seizures.

The people most at risk are endurance athletes who drink large amounts of plain water during long events without replacing sodium, and people with certain medical conditions. If you have heart failure, kidney disease, or liver disease, your doctor may actually want you to limit fluids, so follow their guidance rather than general advice.

Easy Tips to Drink More Water

If you struggle to drink enough, these small habits can help:

1. Start your day with a glass. Drink a glass of water when you wake up, before coffee.
2. Carry a reusable bottle. Having water within reach makes sipping automatic.
3. Pair water with routines. Have a glass with each meal and each time you take a break.
4. Add flavor naturally. Try slices of lemon, cucumber, mint, or berries.
5. Eat water-rich foods. Fruits, vegetables, and soups all add to your fluid intake.
6. Swap sugary drinks. Replacing soda or sweet tea with water or sparkling water cuts calories too, which can support goals like walking for weight loss.
7. Set gentle reminders. A phone alert or an app can help until the habit sticks.

The Bottom Line

So, how much water should you drink a day? For most healthy adults, total fluids of around 11.5 cups for women and 15.5 cups for men, including water from food, is a good general target. Drink more when you exercise, when it is hot, or when you are sick, and use thirst and urine color as everyday guides. If you have a health condition that affects fluid balance, ask your doctor what is right for you.

Staying hydrated also supports your skin and overall well-being. For more, see our guides on coconut water for skin and our glow-up tips that actually work.