Staying hydrated is crucial for overall health, and drinking water is one of—if not the—best ways to do that. So if coffee and tea are made with water, can they count toward your daily water intake or are they just straight up dehydrating?
Because of the caffeine, coffee is both a natural diuretic and a bladder stimulant, urologist Vannita Simma-Chiang, M.D., previously told mbg, and tea has a similar effect. While that's true, the diuretic effects are mild, and research shows that coffee and tea—despite common misconceptions—are not actually dehydrating1 when they're consumed in moderation.
Does a cup of coffee count as a glass of water?
While a cup of coffee is not as hydrating as a glass of water, it can count toward your daily liquid intake. "Because it acts as a diuretic, I would count coffee as about half as much liquid as it really is," physician Catherine Waldrop, M.D., tells mbg. "For instance, one cup of coffee would count as half a cup of water," she explains.
That said, drinking multiple cups of coffee or tea without also drinking water could end in dehydration. "A cup of coffee is not going to dehydrate you that much," integrative medicine doctor Bindiya Gandhi, M.D., says, "but many cups of coffee without water intake will."
Dry, chapped lips could be a sign you've gone overboard, gastroenterologist Will Bulsiewicz, M.D., MSCI, previously explained. Other signs of dehydration include dark yellow urine and not feeling an urge to pee often enough.
Summary: One cup of coffee would count as about half a glass of water.
Does a cup of tea count as a glass of water?
Most teas do contain caffeine but significantly less than coffee. Therefore, Waldrop counts most caffeinated teas as three-quarters of the volume of water. Herbal teas, however, don't contain any caffeine and would, by her standards, be equivalent to a full cup of water.
While these numbers are not based on an exact science, Waldrop says they can be used as general guidelines to make sure your fluid intake is sufficient.
Summary: One cup of tea would count as about three-quarters of a cup of water.
What about flavored coffees and teas?
Different types of coffee and teas will have different effects on hydration levels. Black coffee or tea, for example, will be less hydrating than a latte or a cup of tea with milk or a non-dairy alternative, Gandhi says.
It may be surprising that milk would be a good source of hydration, but it has been shown in some studies to promote rehydration after exercise2—even more successfully than some sports drinks. "Even though lattes would contain less coffee, for reference, I'd still count them as about half [the volume of water]," Waldrop says.
The bottom line.
Overall, coffee and tea don't necessarily counteract hydration4 as many once believed they would, Gandhi says. "Your body will absorb the liquid you consume via teas and coffee as hydration," she adds.
For other ways to stay hydrated, be sure to drink plenty of water—especially when you're exercising, sick, or in any other situation where you may be losing fluids. Eating hydrating or electrolyte-rich foods can also count toward and benefit overall hydration levels.
Abby Moore is an editorial operations manager at mindbodygreen. She earned a B.A. in Journalism from The University of Texas at Austin and has previously written for Tribeza magazine. She has covered topics ranging from regenerative agriculture to celebrity entrepreneurship. Moore worked on the copywriting and marketing team at Siete Family Foods before moving to New York.