Water intake

There's no universal right number or even universal minimum.

As extreme examples, a large person working an intensely physical outdoor job in a hot climate needs lots more than a petite person who works at a quiet desk job in a climate controlled building and lives in a temperate place.

You want to consume enough fluids that your urine is generally pale yellow, like straw color. Very bright yellow that's still light yellow can be OK, too - it can happen with consuming more than needed of some water-soluble vitamins. Very dark yellow to brown-ish urine, that suggests itoo little fluids. Clear urine, too much fluids. Yes, it's possible to drink too much.

What really matters isn't just water, either, it's hydration from all fluids: The water in soup, tea, soft drinks, juices, fruits, and coffee are all considered to be hydrating, according to the most recent research. That's the main reason there's no minimum for plain water, since a person can get enough water from other water-containing foods/drinks.

For most people, thirst is a reasonable guide, with urine color as a double-check.