Quote Originally Posted by Jiffer View Post
they typically say a big sports bottle an hour (24-ish oz.?), but in extreme conditions more. You have to figure out for yourself how much "more" is for you. Better to err on the side of caution.
A simple way to gauge your sweat rate is by weighing yourself before and after a ride. It doesn't tell you how well hydrated you were before, obviously, but it will tell you how much you sweated out. "A pint's a pound the world around," or less poetically, a liter is a kilogram. Empty your bladder before each weighing, take note of how much water you drank, and if your weight has changed, adjust your fluid intake accordingly on your next ride.

Everyone's different. I'll sweat out a liter an hour on a cool-ish day.

I can't over-emphasize how important it is to replace electrolytes when you're drinking lots of water.