How Much Water Should I Drink Per Day?

Q: How much water should I drink to lose weight?

Drinking water does not directly burn fat, but it can support weight loss. Drinking a glass before meals can reduce appetite. Replacing sugary drinks with water eliminates hundreds of daily calories. Staying hydrated also prevents the fatigue and hunger signals that dehydration can mimic. Aim for at least your baseline water target plus extra around meals.

Updated March 2026 · 6 min read · By Travis Cook

You've probably heard the "8 glasses a day" rule. That number is easy to remember, but it's not actually based on strong science. Your real water needs depend on your body size, how active you are, the climate you live in, and what you eat. Here's what the research actually says.

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The Quick Answer: A Better Rule of Thumb

A better rule: take your body weight in pounds, divide by 2, and drink that many ounces. Weigh 160? Aim for 80 ounces (10 cups). Weigh 200? That's 100 ounces (12.5 cups). Simple, scales with your actual body, and way more accurate than "8 glasses" for everyone.

Add 12-16 ounces for every 30 minutes of exercise, more if it's hot. And for every cup of coffee or alcoholic drink, add a glass of water to offset the mild diuretic effect.

What the Science Says

The official NASEM recommendation is 3.7 liters (125 oz) for men and 2.7 liters (91 oz) for women per day. This includes water from all sources: drinking water, other beverages, and food. About 20% of your daily water intake typically comes from food, especially fruits and vegetables like cucumbers, watermelon, oranges, and lettuce.

So the actual drinking target is more like 100 ounces for men and 73 for women. If you exercise regularly, live somewhere hot, or are pregnant/breastfeeding, go higher.

Daily Water Intake by Body Weight

Body Weight	Baseline (oz/day)	Active / Hot Climate
120 lbs (54 kg)	60 oz (1.8 L)	72 - 84 oz
140 lbs (64 kg)	70 oz (2.1 L)	84 - 98 oz
160 lbs (73 kg)	80 oz (2.4 L)	96 - 112 oz
180 lbs (82 kg)	90 oz (2.7 L)	108 - 126 oz
200 lbs (91 kg)	100 oz (3.0 L)	120 - 140 oz
220 lbs (100 kg)	110 oz (3.3 L)	132 - 154 oz

Where the "8 Glasses" Rule Came From

The 8-glasses thing traces back to a 1945 report that recommended 2.5 liters of water per day. What everyone ignored: the report also said most of that would come from food. The simplified version stuck anyway and became gospel despite having no real scientific backing.

Signs You Are Not Drinking Enough

Thirst is the obvious one, but it's unreliable -- especially as you get older, your thirst signal weakens. Better indicators: dark yellow urine (you want pale straw), dry mouth, headaches, fatigue, brain fog, or getting dizzy when you stand up. Check your urine color. If it's consistently dark, drink more. Simple as that.

Can You Drink Too Much Water?

Yes, technically. Hyponatremia happens when you drink so much that your blood sodium crashes. It's mostly a risk for marathon runners and endurance athletes who guzzle water for hours without replacing electrolytes. Your kidneys can handle about a liter per hour. Unless you're chugging water competitively, this isn't something to worry about.

Does Coffee Count as Water?

Yes. This surprises people, but coffee and tea count toward your water intake. Caffeine is a mild diuretic, but the water in the cup more than makes up for it. One cup of coffee hydrates you almost as well as one cup of water. The Frappuccino with 400 calories is a different story, but black coffee is basically water with benefits. If you're curious about how much caffeine you're consuming, check our Caffeine Calculator.

Practical Tips for Drinking More Water

Carry a water bottle everywhere. If water is within arm's reach, you'll drink it without thinking. Get one you actually like and keep it filled.

Drink a full glass first thing in the morning. You wake up dehydrated after 7-8 hours with no water. One glass before coffee resets the baseline.

Eat your water. Watermelon, cucumbers, strawberries, and oranges are 90%+ water. Soups and smoothies count too. You don't have to get everything from a glass.

Set reminders if you forget. Hourly phone reminders feel silly for about a week, then the habit sticks and you won't need them.

Flavor it. Lemon, cucumber, mint, berries. Sparkling water counts. Skip the sugar-loaded enhancers if you can.

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About the Author

Travis Cook writes about health and wellness for MayoCalc. With a background in radiology and clinical imaging, Travis translates peer-reviewed medical research into practical guidance backed by data from the ADA, AHA, ACC, and CDC. All health content is sourced and linked so you can verify every claim.

Hydration FAQ

Is 8 glasses of water a day enough?

For some people, yes. For others, no. Eight glasses equals 64 ounces, which may be enough for a smaller, sedentary person but insufficient for a larger or active person. A more accurate guideline is half your body weight in ounces per day, adjusted for activity and climate.

How much water should I drink to lose weight?

Drinking water doesn't directly burn fat, but it can support weight loss. Drinking a glass before meals can reduce appetite. Replacing sugary drinks with water eliminates hundreds of daily calories. Staying hydrated also prevents the fatigue and hunger signals that dehydration can mimic. Aim for at least your baseline water target plus extra around meals.

What color should my urine be?

Pale straw or light yellow indicates good hydration. Clear urine may mean you're overhydrating. Dark yellow or amber indicates dehydration. Check your urine color in the morning for the most reliable reading.

Does sparkling water hydrate you?

Yes. Sparkling water hydrates just as well as still water. The carbonation doesn't affect hydration. Choose plain sparkling water over flavored varieties that may contain added sugar or sodium.

How much extra water do I need when exercising?

Drink 12 to 16 ounces of water for every 30 minutes of moderate exercise. For intense exercise lasting over an hour, consider adding electrolytes to replace sodium and potassium lost through sweat. Weigh yourself before and after exercise; drink 16 to 24 ounces for every pound lost.

For more on this topic, see our sleep guide.

Sources

National Academy of Medicine: Dietary Reference Intakes for water and electrolytes
Mayo Clinic: Water intake recommendations and hydration guidance

Related Tools

Get your personalized target with the Water Intake Calculator, check your caffeine intake with the Caffeine Calculator, or find your daily calorie needs with the Calorie Calculator.

Disclaimer: This article is for general information and is not medical advice. Individual water needs vary based on health conditions, medications, and other factors. Consult a healthcare provider if you have concerns about your hydration or have a condition that affects fluid balance.