You'll find as your conditioning improves one bottle should be enough for a moderate (course & temperature) 30mile ride. Anything longer than that and you might want two bottles. I suggest you get a second bottle, but you'll find more liquid left over as you get stronger. I take two bottles when ever I group ride because I ride 7.5miles to and from the start point. The ride itself is either 28 or 42miles depending on what I'm in the mood for.