No one will ever be able to answer that question unless you already know the weight of the yarn. Typically yarn is sold with an indication on the label as to how many grams there are per how many yards. So you will see something similar to this, 300g/162yds. So your pattern is going to be very difficult to determine how much you are truely going to need.
I hate patterns that list things like that. What if you end up with a really heavy yarn, depending on the fiber used to create them the weight could vary for even the same thickness of yarn. So 300g in one yarn is not the same length as 300g in another type of yarn. Eventually you will sort of learn to eyeball your projects and see how much they might need. For now, it would be best to post the project and possibly a picture of what you'll be knitting so that we can see it and give you an estimation.