About you
Answer these and we'll calculate your daily target.
This is your total daily water target including drinks and water-rich foods. About 20% comes from food (fruits, vegetables, soups), so aim for ~80% of this from beverages.
How we got there
That's 10 glasses spread across your day
Aim to drink steadily, not all at once. A glass when you wake, with each meal, and at intervals between is the easiest pattern to hit your goal.
Where will all that water come from?
Bottled water gets expensive fast. See how a home filter compares for your household's daily intake.
Tools that help you actually drink it
32oz insulated bottle
The single best hydration upgrade. Hydro Flask, Yeti, or Stanley — fill it twice and you're at 64 oz without thinking. Insulated keeps water cold all day.
See on Amazon →Motivational water bottle
Marked with hourly targets so you don't fall behind. Especially helpful if you forget to drink during work — visual reminders force the habit.
See on Amazon →Brita filter pitcher (10-cup)
If your tap doesn't taste great, you'll drink less. A simple pitcher filter dramatically improves drinking compliance — for under $40.
See on Amazon →Electrolyte powder
If you exercise hard or sweat a lot in heat, plain water isn't enough. Sodium and potassium replacement matters. LMNT, Liquid I.V., and Nuun are the popular picks.
See on Amazon →Understanding hydration
The "8 glasses a day" rule — outdated?
"8 glasses a day" (64 oz) is a popular rule but doesn't fit everyone. It's roughly right for an average sedentary adult woman in a temperate climate — and very wrong for a 220-lb athlete in Phoenix.
The National Academy of Medicine actually recommends about 125 oz total daily intake for men and 91 oz for women, including water from foods. Adjusted for what comes from food (typically 20%), that's still 100 oz from beverages for men, 75 oz for women — both higher than 8 glasses.
This calculator uses your specific body weight as the starting point (0.5 oz per pound) and adjusts for everything else. It's more accurate than any single rule of thumb.
What counts as water intake?
Plain water: The gold standard. No calories, no caffeine, no diuretics — pure hydration.
Tea and coffee: Yes, these count. Despite caffeine being a mild diuretic, the water content easily exceeds the loss from caffeine. Studies show moderate caffeine intake (under 400mg/day) doesn't cause dehydration.
Milk, juice, sports drinks: Count toward hydration but bring calories or sugar. Use sparingly.
Sugary sodas: Hydrate but the sugar load can outweigh benefits. Try not to count these.
Alcohol: Net negative. Each alcoholic drink causes you to lose more water than the drink contains. Compensate with extra water (this calculator does this for you when you mark it as a special situation).
Water from food: About 20% of daily water typically comes from fruits, vegetables, soups, and other water-rich foods. Watermelon is 92% water, cucumber 95%, soup ~90%.
Signs you're drinking enough (or not)
The urine color test: The most reliable real-time indicator. Pale yellow = well hydrated. Dark yellow or amber = drink more. Clear urine = possibly overhydrated, especially if frequent.
Thirst: By the time you feel thirsty, you're already mildly dehydrated (1–2% body water loss). Don't wait for it.
Headaches: A common sign of mild dehydration, especially afternoon headaches at desk jobs.
Fatigue and brain fog: Even 1–2% dehydration measurably reduces cognitive performance.
Dry mouth, lips, skin: Late-stage signs — by here, you're significantly behind.
Dizziness, rapid heartbeat: Severe dehydration. Drink water and consider electrolytes; if it persists, seek medical attention.
Can you drink too much water?
Yes — but it's hard to do accidentally. Hyponatremia (water intoxication) happens when you drink so much water that your blood sodium drops dangerously low. Generally requires 10–15+ liters in a short time, far beyond normal intake.
Most cases of hyponatremia are athletes during very long endurance events (marathons, ultras), people on certain medications (some psychiatric meds, MDMA), or people with kidney issues. For a healthy adult drinking water normally throughout the day, it's not a concern.
If you're an endurance athlete, focus on electrolyte replacement during long efforts — don't just chug water. For everyone else, listen to your thirst (and aim for the recommendation above as a target, not a minimum).
The Home Water Guide is reader-supported. We may earn commission on linked products. Calculations based on guidelines from the National Academies of Sciences (Institute of Medicine) and American College of Sports Medicine. Individual needs vary — this estimate is a starting point, not medical advice.