The formula
A = P(1 + r/n)^(nt), where P is the starting amount, r the yearly rate, n the compounding periods per year and t the years. Monthly contributions are added at the end of each month.
Frequently asked questions
What is compound interest?
Interest earned on both your original money and on interest already earned, so growth speeds up over time.
Does compounding frequency matter?
More frequent compounding earns slightly more, but the rate and time invested matter far more.