How many watts does an Apple USB Power Adapter use?

I am thinking of taking it to Europe with me this summer, and using my iPod touch as well with it (First generation). I am looking at voltage converters, and most have wattage limits on them. How many watts does an Apple USB Power Adapter (the small one that is now included with iPhone 3Gs)? For more info - http://store.apple.com/ca/product/MB352LL/B?mco=MzE4NjMwNA But then again, on the actual thing itself, it says voltage 100-240 volts. Does this mean that I DO NOT need a voltage converter, but just an actual plug that will change my rectangle prongs into cylinder type prongs?