Compound interest calculator
Explore how a starting amount, regular contributions, time, and a constant return assumption affect a hypothetical balance.
Your assumptions
How the calculation works
FV = P × (1 + r)^n + C × ((1 + r)^n − 1) / rP is the starting amount, C the month-end contribution, r the nominal annual rate divided by 12, and n the number of months. At a zero rate, the result is simply P + C × n. Real investment returns do not arrive as a steady monthly interest rate.
Questions, answered.
Is the annual rate a forecast?
No. It is an assumption you enter. Real returns can vary substantially and can be negative. Compare several scenarios rather than treating one number as a prediction.
When are contributions added?
At the end of each month, after that month’s growth. A whole number of months is used; fractional years are rounded to the nearest month.
Does this include fees or inflation?
No. The result is nominal and excludes fees and taxes. The same nominal amount may buy less in the future.
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