How much water should I drink a day?

There's no single number for everyone. As a population guide, the U.S. National Academies set an adequate total-water intake of about 3.7 liters/day for men and 2.7 liters/day for women, and that includes water from food, not just what you drink. Most healthy people meet their needs simply by drinking to thirst. This tool gives a personalized starting estimate from your body weight, activity, climate, and exercise, as an educational ballpark, not a medical prescription.

Do I actually need electrolytes, or just water?

For an ordinary day, plain water and normal meals usually cover it. Electrolytes start to matter when your losses or intake shift: heavy sweating or heat, low-carb/keto flushing sodium, eating much less on a GLP-1, or illness. The tool flags when your situation makes electrolytes worth attention, and when it doesn't.

Does coffee or tea count toward my water intake?

Yes. For most people, the fluid in coffee, tea, and other beverages counts toward daily hydration, and food contributes water too. A lot of coffee or alcohol does increase output, so it's easy to under-replace on a heavy day, which is why the tool adds a small buffer when you flag that.

The Boring Thing. Free Hydration Tool

How much water, and do electrolytes matter for you?

"Drink 8 glasses" ignores your body, your day, and your situation. This turns it into a real daily number, and tells you plainly when electrolytes, not just water, start to matter.

Estimated daily water target

–oz

Enter your weight to estimate it.

Do electrolytes matter right now?

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Toggle your situation below to find out.

Your number depends on your body and your day, not a one-size rule.

About you

A few honest inputs make the estimate yours instead of a generic rule of thumb.

Body weight

Units

Activity level

Hard exercise (minutes/day that make you sweat)

Climate

Your situation

These shift how much you lose, or how much you take in. They're what decide whether electrolytes matter for you, not just plain water.

Sweating a lot / heat exposure today Long workouts, manual labor, sauna, or a hot day outside. Low-carb or keto Lower carbs flush more sodium and water, so losses run higher. On a GLP-1 / eating less than usual When intake drops, the water & minerals food normally provides drop too. A lot of coffee or alcohol today Both increase fluid output, so it's easy to under-replace. Feeling under the weather Fever, sweating, or an upset stomach raise fluid and mineral losses.

The formula, in plain terms (and why it's an estimate)

Baseline: we start from roughly 30–35 ml of water per kg of body weight per day: a common general guideline. We use ~33 ml/kg, nudged up for a warmer climate and for activity level. Exercise: we add about 350–500 ml per 30 minutes of hard, sweaty activity. Coffee/alcohol add a small replacement buffer. The result is shown in ounces (or liters), with food and other drinks counting toward it. This is a general educational estimate. Real needs vary a lot person to person, and certain conditions (kidney, heart) change the picture entirely, so a doctor's guidance comes first.

When do electrolytes matter, not just water?

Plain water is usually plenty for an ordinary day. The math changes when you're losing more (heavy sweat, heat, illness) or your intake has shifted (keto flushing sodium, or eating much less on a GLP-1), because then you're down on water and on the sodium, potassium, and magnesium that normally come with food and steady intake. That's when adding electrolytes, alongside water, can be worth attention. This tool flips the verdict to YES when any of those situations are on.

Read: the signs of dehydration →

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General educational estimate, not medical advice. Hydration needs vary; certain conditions (kidney, heart) require a doctor's guidance: consult a healthcare provider, especially if on medication or a GLP-1. This tool does not diagnose, treat, cure, or prevent any condition. Baseline assumes ~33 ml/kg/day adjusted for activity, climate, and exercise; food and other beverages count toward your total. For context, the U.S. National Academies set an adequate total-water intake of about 3.7 liters/day for men and 2.7 liters/day for women (including water from food); most healthy people meet their needs simply by drinking to thirst. Source: National Academies of Sciences, Engineering, and Medicine.