Staying hydrated is essential for your health, particularly when you're working out and possibly losing a lot of water through sweat. This infographic from Greatist and CamelBak take the mystery out of how much water you need to drink, depending on the kind of exercise you do and other factors.
As the graphic points out, general guidelines are to drink 17 to 20 ounces (500-600ml) of water 2 to 3 hours before exercising, another 8 ounces (250ml) glass during your warm-up (or 20 to 30 minutes before exercising), 7 to 10 ounces (200-300ml) every 10 to 20 minutes during exercise, and 8 ounces (250ml) of water within 30 minutes after exercising. Yes, that's a lot of water!
How much you need to drink, however, depends on your age, gender, height, weight, exercise intensity, and how long you exercise. People who sweat a lot may need to drink more. The graphic includes example water amounts for men and women and several other hydration tips. For a more accurate calculation, check out CamelBak's Hydration Calculator (which takes into account the colour of your pee). Instead of water, though, may I suggest a glass of low-fat chocolate milk for your post-exercise drink?
Here's the full graphic: