Everyone has this problem if you are not an Excel Master.
Here is how you fix this.
Highlight all of the data that you want to print. Click on File>Print, and check the box that says selection. Then click on Preview. You can adjust it from there either by expanding your margins or by clicking on setup.
The reason it is so small is that it is trying to print the entire page, even the blank spaces. By selecting the print range, and hitting selection when you print, you will not have that problem.
Side Note...In the upper left hand side of your screen you will see a drag down. The field looks like a cell designation with a down arrow next to it. Once you select your print range, drag that box down, and type in "Print". From that point on you have "Named" that Range. When you drag that selection down, you will see the word "Print", click on that and it will automatically select your print range as well as your print settings.
This is not real easy to explain, but it is quite simple.
Good luck.....Feel free to email should you have more questions regarding Excel.
Made on a Mac!!!!