Hydration 101

Our bodies are 60% water, so getting enough to drink every day helps with everything from regulating our temperature and keeping our joints moving smoothly, to protecting our spinal cord and getting rid of waste. Being even a little dehydrated is not good. Studies have shown that losing just 1 to 2% of our bodyweight without replacing fluids makes it hard to think straight and remember things. Even worse: A 4% fluid deficit causes headaches, irritability, and sleepiness (we’ve all been there). If you’ve ever tried to conquer a tough workout without properly hydrating, you know it impairs muscle endurance and strength, too.

So how much water do you need in a given day, and how do you know if you’re not getting enough? This quiz—along with the answer key at the end—contains all the info you need to keep yourself calm, cool, and well-hydrated. Let’s see what you know.