Compound Interest Functions
Some helpful functions

I participate in my company's 401(k) plan.
How much will be in my account at some future date?

I need money paid to me at certain intervals in the future, such as for college tuition for my child, or for retirement income for myself.
How much will I have to save to do this?

I have a monthly mortgage payment, and plan to pay an extra amount towards the principal.
How much sooner will it be paid off?

I want to retire someday.
How much should I be saving now?

 Interest rates have dropped, and I may refinance my mortgage.
How soon can I recoup the refinancing costs?