When it comes to the size of your backpack, bigger isn't necessarily better. The size of your bag comes down to how much stuff you're going to be taking with you. Many first time backpackers tend to pack way too much stuff and end up buying an unnecessarily big backpack. Backpacks come in sizes ranging from 35L to over 100L. The trick is to find a bag that is the right size for you. If it's too small then it'll be challenging to fit everything you need into it and if it's too large then it's going to be bulky, heavy and cumbersome. If you pack properly, you should easily be able to fit everything you need for your trip into a bag in the 50-70L size range.