Hydration basics

How Much Water Should You Drink a Day?

By the Fresh Alka Water family · October 16, 2026 · 4 min read

You've probably heard "eight glasses a day." It's a good, easy goal, but most adults need a bit more total fluid than that. Here's what the experts actually recommend.

The short answer

The U.S. National Academies of Sciences, Engineering, and Medicine set an adequate daily intake of total water of about:

• 15.5 cups (3.7 liters) a day for men
• 11.5 cups (2.7 liters) a day for women

Those numbers come from the National Academies' Dietary Reference Intakes and are the same figures Mayo Clinic uses. They count all fluids, including water from food, which makes up roughly 20 percent of the total for most people. So a typical adult drinks somewhere around 9 to 12 cups of actual beverages a day, and plain water is the best choice for most of it.

What that looks like in gallons

There are 16 cups in a gallon. If you drink about 8 to 12 cups of water a day, one person goes through roughly a gallon every day and a half to two days. A household of four drinking mostly water can easily use a 5-gallon jug in a week or less, before counting coffee, tea and cooking.

When you need more

Mayo Clinic lists several things that raise how much you need:

• Exercise. Drink before, during and after any activity that makes you sweat.
• Hot or humid weather. You sweat more, so you need more. Inland San Diego heat waves count.
• Illness. Fever, vomiting or diarrhea all cause you to lose fluid.
• Pregnancy and breastfeeding. Both increase fluid needs.

The simplest check

Your body gives you two easy signals. If you rarely feel thirsty and your urine is pale yellow or clear, you're likely drinking enough, according to Mayo Clinic.

Make it easy

The CDC suggests carrying a reusable water bottle and choosing water over sugary drinks. Keeping a full jug in the fridge at home and a bottle in the car is the easiest way we know to hit your number without thinking about it.

This article is general information, not medical advice. People with heart, kidney or liver conditions sometimes need to limit fluids, so ask your doctor what's right for you.