Here you'll find dozens of financial calculators that are easy-to-use yet flexible and, most importantly, accurate. Unlike many other online calculators, the ones here are date sensitive, and many even support changes to interest rates, amounts, and date sequences. While other websites offer you "estimates," the below calculators will provide you with accurate results. They are not toys; they are the real deal.
The Ultimate Financial Calculator is the calculator you should be using, for example, if you need to model complex cash flows; perform analytics (PV, ROR, etc.) on a cash flow; or calculate a loan payoff or investment balance as of a specific date. Here are 25 calculation tutorials to get you started. The other calculators give you somewhat less control over dates and rates in exchange for ease and speed of use.