Maybe you're the type of person who takes forever to tally up numbers (probably because you have to double- and triple-check your math), or maybe someone in your family finally enrolled in an advanced math class. Either way, you need a calculator, and you're looking at eBay for a deal on a new or gently used one. There's more to these devices than the 10-digit clunker you had in elementary school. A basic scientific calculator covers all the functions you need for a basic or intermediate math class. These include basic scientific notation, logarithmic functions, and exponential functions. For more advanced math, you might need to use a graphing calculator. Like the name implies, these handle graphing as well as plotting, in addition to the same functions as a scientific calculator. Choose a calculator not just for what it can do, but the specs it offers—advanced machines have a lot of memory and features like rechargeable batteries. Before purchasing a calculator for a class, check with your instructor or syllabus to see whether a specific calculator is recommended for the course. Choosing the right calculator not only makes solving math problems easier, but also helps you visualize and understand advanced concepts. And even if you are numerically challenged, you don't need a calculator to calculate just how much time you'd save by using one.