The National Academies of Sciences recommend about 3.7 liters (for men) and 2.7 liters (for women) total per day. But here’s the kicker: that includes water from food and other drinks. Your coffee counts. Your soup counts. That juicy peach counts.
So, a good starting point is to aim for half an ounce to an ounce of water per pound of body weight. If you weigh 150 pounds, try 75-150 ounces daily. But start at the low end. You can always add more if you’re feeling dry or working out.