Compound interest calculator
Put in a starting amount, what you add each month, a rate and a number of years. You get the final value, the interest earned and the balance at the end of every year.
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Balance at the end of each year
Questions people ask
What formula does this use?
It steps through one month at a time rather than using a single closed formula, because the monthly
deposit changes the balance as it goes. Each month:
new balance = old balance × (1 + i) + deposit, where i is the yearly
rate ÷ 12 ÷ 100. With no deposits that is the same as
final = P × (1 + i)^n over n months.
When is the monthly deposit added?
At the end of each month, so the deposit you make in a month earns nothing that month and the very last one earns nothing at all. That is the cautious assumption. If your account compounds yearly, quarterly or daily, or you pay in at the start of the month, your real figure will differ a little.
Does the result allow for inflation, tax or fees?
No. It is a plain nominal figure. Tax on interest, fund charges and inflation all pull the real result down, and none of them are in the number above. For a rough inflation-adjusted view, subtract expected inflation from the return before you type it in: 7% growth with 3% inflation becomes 4%.
Not financial advice. This calculator is for information only. The results are estimates and investment returns are never guaranteed. A fixed yearly return is an assumption, not a prediction. Check any figure that matters with an advisor.