Compound interest can work to your advantage as your investments grow over time, but against you if you're paying off debt, like credit cards.

Doing the math and crunching the numbers when it comes to figuring out your loan's interest can be complicated. Here's how to calculate interest on a loan.

We can let compound interest help us get there with our short-term savings and the compounded growth of long-term stock investing can help with the rest.

If you're new to the idea of how compounding interest works, here's a quick overview and how it can help you retire as a millionaire, even while earning a modest income. Image source: Getty Images.