How it works
Formula
The balance is simulated month by month. Interest compounds at the frequency you choose, converted to an equivalent monthly rate (1 + APR/k)^(k/12) − 1, so monthly contributions earn interest consistently. With monthly compounding and end-of-month deposits this equals the textbook formula FV = P(1+r)^n + PMT·((1+r)^n − 1)/r.
Frequently asked questions
What return should I assume?
Savings accounts and CDs publish an APY. For stock investments, past returns do not guarantee future results; try several rates to see a range.