Your body needs water to function, and that doesn’t stop when the weather starts cooling down in the fall and winter. But exactly how much water should you be drinking every day?
You’ve probably heard the “8 by 8” rule, which states that you should drink eight 8-ounce glasses of water each day. However, according to Renee Fitton, registered dietitian and director of education at nutrition technology company L-Nutra, “The 8 by 8 rule can be a bit oversimplified for some, but it’s also not necessarily dangerous.”
This is what experts say is the amount of water you should actually be drinking every day.
How much water should you drink every day?
Fitton says various factors affect the amount of water one needs daily, including body size, medications, gender, physical activity, climate, health status and altitude.
Most of us are also familiar with the old adage: Drink eight 8-ounce glasses of water daily. The eight-by-eight rule advises us to drink 64 ounces (approximately 1.9 liters) of water daily. Many of us have blindly followed this advice for our entire lives, without knowing its origin or the rationale behind the recommendation to drink eight glasses of water.
Apparently, the eight-by-eight rule came out of a void, because there’s no scientific evidence to back it up. It’s just another of those long-standing myths people believe because that’s what everyone believes. Drinking 64 ounces of water daily isn’t bad, but it could be too much or not enough for some people.
“For some people, simple rules like these help them stay on track. If drinking eight 8-ounce glasses of water a day helps someone hit their hydration goals, then it’s a fine starting point. But I wouldn’t call it the gold standard,” says Fitton.
Other guidelines exist but there’s still no true consensus. There’s no formal recommendation for how much water people should drink daily, perhaps because everyone needs different amounts of water.
An “adequate intake” of water for adult men and women does exist but it can vary from person to person. This adequate intake includes water from nonwater beverages, such as milk, sports drinks, tea and yes, even coffee. It also includes water from fruits, vegetables and other foods (think of how much water goes into a bowl of oats or soup).
The adequate intake is 15.5 cups (3.7 liters or 125 ounces) for average men and 11.5 cups (2.7 liters or 91 ounces) for average women. How you choose to consume these 125 or 91 ounces of fluid is up to you. Although this is the closest figure we have to a recommended daily intake, even these numbers differ for each person based on their health condition.
Reasons why you may need to drink more water
You have an active job: Those on the go all day (especially folks who work outdoors) may need more water than most people. The more you move, the more you sweat, and you should replace lost water (and electrolytes) through fluid intake.
If you are working outside during a heat wave, the US Centers for Disease Control and Prevention recommends drinking 8 ounces (1 cup) of water every 15 to 20 minutes during work. Drinking water before and after work can help prevent dehydration.
You exercise often: If you don’t have an active job but you do exercise a lot — whether in the gym or through recreational activities — you also need more water than most. Even if you don’t realize it, you lose a lot of fluids during physical activity (even in cold weather). Up your water intake to account for activity (especially travel activity).
You live in a hot climate: Hot weather means increased sweating and replacing the lost fluid is important. Dryness compounds fluid loss in hot weather — people in desert climates may need more water than those in tropical climates.
You’re pregnant or breastfeeding: Pregnant women need more water to encourage improved circulation, increased calorie intake and other physiological processes that support their baby’s growth. Breastfeeding women need extra water to support breast milk production.
Your urine is dark in color: The color of your urine can tell you a lot about your hydration levels. “The color of your urine is the best and most personalized, consistent and immediate way to measure hydration throughout the day. We want to look for light yellow pee, not fully clear (over-hydrated) but also not deep yellow or amber (under-hydrated),” says Fitton.
You have a dry mouth, chapped lips or muscle cramps: Yep, when you are dehydrated your body will let you know. “Water is such a critical substance for life so when we’re lacking, our body will no longer work at its peak capacity and this can persist in many ways and uniquely from one person to another,” Fitton says.
Hydration hacks to help you drink more water
Different people follow different rules for hydrating. These four common guidelines can help you stay hydrated no matter your lifestyle.
Drink when you’re thirsty
There’s some controversy surrounding this method. Some health professionals say you shouldn’t overcomplicate hydration and your body tells you when it needs water. Others say waiting until you’re thirsty is waiting too long — that you’re already dehydrated when you feel thirsty. Some people seem to have stronger thirst mechanisms than others so this method may not work for you.
Drink a glass before meals and between meals
This isn’t bad advice. Structuring water intake around a ritual like mealtime can ingrain hydration as a habit. Your total water intake will vary depending on how many meals you eat. If you eat three meals, you’ll drink five glasses of water according to this rule, which may not be enough (unless they’re big glasses). This rule probably won’t work for you if you don’t have a routine eating pattern.
Drink eight glasses daily
Generic health advice rarely works for everyone. If you feel adequately hydrated on 64 ounces of water each day, then that amount is likely sufficient to keep you hydrated. If you feel overly hydrated (clear urine, very frequent urination or swelling), cut back slightly. If you feel dehydrated (dark urine, headaches, infrequent urination, lightheaded or fatigue), eight glasses may not be enough for you.
Drink half your body weight in ounces
This is a simple guideline that’s easy to remember and usually easy to achieve. If you weigh 150 pounds, aim to drink 75 ounces of water each day. This is the only rule of thumb that accounts for different body sizes but it doesn’t account for thirst, climate, activity level or other factors.
Make water visible and accessible
Fitton says that keeping your water accessible at all times provides a visual reminder to drink water. She also recommends using an app like WaterMinder that sends daily reminders to drink water.
Pair your water intake with your daily habits
Another great way to get your daily water intake is to make drinking water part of your daily habits. This can look like drinking water right when you wake up, after eating a meal or right before you leave the house. “These mini habits build on things you already do, so you’re not trying to remember to do something new. The more you tie hydration into your daily routine, the easier it becomes,” says Fitton.
Experiment with hydration techniques to find what works for you. As long as you’re not battling chronic fatigue, lightheadedness, headaches or other signs of dehydration, you are probably doing a pretty good job. As a failsafe, you can always determine whether you are under or overhydrated based on the color of your urine.
