Finance
Compound Interest Calculator
See how your savings or investment grows over time with monthly compounding and optional monthly contributions.
How this is calculated
Interest compounds monthly on the starting amount and on every monthly contribution, which is how most savings accounts, index funds, and retirement accounts are modeled. Actual investment returns vary and are never guaranteed.
Why time matters more than amount
Compounding is exponential: the interest you earn starts earning interest of its own. Ten years of contributions starting today will usually beat a much larger sum invested ten years from now, which is why starting early matters more than starting big.