Most healthy adults should aim for around 2–3 liters (about 8–12 cups) of fluids per day, with men typically needing more than women and exact needs changing with activity level, climate, and health.

Core daily targets

  • Men: about 3–3.7 liters of total fluids per day (roughly 13–15.5 cups).
  • Women: about 2–2.7 liters of total fluids per day (roughly 9–11.5 cups).
  • About 20% of this usually comes from foods (fruits, vegetables, soups), not just plain water.
  • “8 glasses a day” is a simple rule of thumb, but many adults actually need a bit more than that.

In practice, “how much should you drink per day” means “how much total fluid (all drinks + water‑rich foods) your body gets in a day,” not just glasses of plain water.

When you need more (or less)

Your ideal intake shifts with your situation.

  • You likely need more if:
    • You exercise or sweat a lot.
    • You work in hot or very dry environments.
    • You have fever, vomiting, or diarrhea.
    • You are pregnant or breastfeeding. (Targets often rise to ~10–13 cups per day. )
  • You may need less or tailored advice if:
    • You have kidney, heart, or certain hormonal conditions.
    • You’ve been told to restrict fluids by a clinician.

Simple self-checks (thirst vs. numbers)

Many experts emphasize using your body’s signals rather than obsessing over a fixed number.

  • Thirst: feeling thirsty regularly is a sign to drink more, but thirst can be blunted in some people (older adults, certain meds).
  • Urine color:
    • Pale straw/light yellow = usually well hydrated.
    • Dark yellow/amber and strong-smelling = drink more.
  • Symptoms of being under‑hydrated can include dry mouth, headache, low energy, dizziness, and infrequent urination.

At the same time, routinely forcing huge amounts of water far beyond thirst and comfort offers little proven benefit for most healthy people.

Can you drink too much?

Overdoing water is uncommon but possible, especially if you chug large volumes in a short time.

  • Extremely high intake can dilute sodium in the blood, leading to headache, confusion, seizures, or worse in severe cases.
  • In healthy people with normal kidneys, the dangerous range is very high (around 10–20 liters a day), but it illustrates that “more” is not always better.
  • Very strict “water challenges” or “cleanses” that push constant drinking without listening to your body are not advisable.

Forums, trends, and real life

Online discussions and “hydration challenges” often push large bottles and strict regimens (like finishing multiple liters every day) as a route to better skin, weight loss, or “detox.”

  • Evidence that drinking beyond normal needs dramatically improves weight, energy, or skin is surprisingly limited.
  • Some studies show modest help with weight loss when people drink water before meals as part of a calorie‑controlled diet, but the effects are small compared with overall eating patterns.
  • Forum threads often include the advice to “just drink when you’re thirsty,” which matches a lot of current research for healthy adults, with the caveat that certain groups (older adults, athletes, people with specific conditions) may need more structured guidance.

TL;DR: For most healthy adults, 2–3 liters (about 8–12 cups) of total fluids per day is a solid target, adjusting up for heat and exercise and down if a health professional has given you limits. Listen to thirst, check urine color, and avoid extreme “water challenges.”

Information gathered from public forums or data available on the internet and portrayed here.