When you’re sweating hard at the gym, it’s a no-brainer that you need to double down on your H2O intake. Ditto if it’s the weekend and you’re out in the summer heat. But what about the majority of the time, when you’re just sitting inside a climate-controlled office?

Of course, if you don’t get enough to drink during the work day, you won’t think as clearly, might start feeling tired, and can get a headache. But as it turns out, hydration’s not as clear-cut as the old (and, some argue, untrue) “eight glasses of water” rule would lead you to believe. There are actually tons of factors that influence how much you need to drink on any given day, from the foods you’ve eaten to your pre- and post-work plans.

To get the facts straight, I consulted sports dietitian Marie Spano, MS, RD. She was a font (no pun intended) of information—and busted one super common water-realated myth while she was at it.

Scroll down for everything you need to know about staying hydrated during the day.

The color of your urine isn’t the best way to keep track of your hydration

“According to the Institute of Medicine, women need about 11 cups of liquid a day to stay hydrated, and that includes all sources of fluid—including food,” Spano says. But considering coffee, tea, citrus fruits, smoothies, and even yogurt all count toward the hydration goal, it’s not like you have to be sitting at your desk chugging water to keep functioning.

Of course it’s pretty tricky to keep close track of how many cups you’re drinking (and eating), unless you’re using this app or you have a hydration tracker (I tested Ulla, which clips to any cup or water bottle and blinks if you haven’t taken a sip at least every 20 minutes, but stopped paying attention to it a few hours into the work day).

The best way to know if you’re staying hydrated? By making a mental note of how often you’re heading to the bathroom. “You should be going every two to three hours,” Spano says. “And you should be producing a good amount of urine, not just a few drops.”

A lot of people assume that if their urine is almost clear, they are well-hydrated, whereas if their urine is dark yellow, they need to drink more. Spano says this is a total myth.

“There are just so many factors within food, including B vitamins, that can make your urine yellow,” she says. “Think about food dye. I had an athlete one time tell me his urine was bright neon—it was because he was drinking so much Gatorade!” The takeaway here: go by frequency, not color. (Also: gross!)

If you never feel thirsty, reach for a sports drink

Some people dutifully have their water bottle on a pretty coaster next to their computer and get up to refill it every couple of hours. Other people, well, they’re just not thirsty, okay?! Spano says those in the latter group could benefit by snacking on something with a little sodium or keeping a low-sugar sports drink handy.

“Sodium stimulates thirst, which is a good thing if you tend to not drink enough,” she says. “And sports drinks with added sodium help retain extra fluid—that’s the whole point of them—so if you’re not well hydrated to begin with, it might not be a bad idea to have some around.” Just be sure to stay away from these.

Drink a little extra if you’re working out that day

Whether you’re an a.m. gym-goer or you like to sweat it out after work, Spano says you need a little extra hydration on the days you’re working out.

“Anyone who exercises needs more fluid, but the exact amount changes based on whether you’re working out inside or outside, the altitude, how long the workout is, and the intensity,” she explains.

Bringing a water bottle to work will ensure you have something to sip on all day—and at the gym. Find one with a design and function you really love. That way, filling it up before you head out the door will be a no brainer, and you won’t be stuck spending $2 on a plastic bottled water later on.

If you’re sitting at your desk wondering when your promotion is coming along, you might want to take a vacation. (Or fake it by sipping on some spa water.) Still feel like quitting? Maybe you should go for it—something amazing just might happen.