Walmart, Target, etc. carry them for around 12 dollars. If you don't have one, try to get one on sale during the back to school sales. They will be marked as "scientific" calculators. Try not to get the ones that say they are for statistics. Stats calculators will just get you confused. I like the TI-30xa. You can also rent a graphing calculator for the year from the media center- a good option if you need one for your math class.