Compound Interest Calculator
Calculate compound interest with regular contributions over time.
About Compound Interest
Compound interest is one of the most powerful concepts in finance. Albert Einstein reportedly called it the "eighth wonder of the world." When you invest money and earn interest, that interest also earns interest in subsequent periods, creating an exponential growth effect. This calculator uses the standard compound interest formula A = P(1 + r/n)^(nt) combined with regular monthly contributions to show you exactly how your investments can grow over time. All calculations run entirely in your browser — nothing is sent to any server.
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Frequently Asked Questions
What is compound interest?▾
Compound interest is interest calculated on the initial principal and also on the accumulated interest from previous periods. It's often described as "interest on interest," and it makes your money grow faster than simple interest.
How does compounding frequency affect returns?▾
The more frequently interest is compounded, the more total interest you earn. Monthly compounding yields slightly more than quarterly, and quarterly yields more than annual compounding — though the difference becomes smaller at lower rates.
Is this calculator accurate for real investments?▾
This calculator provides an approximation based on a constant rate of return. Real investments may fluctuate in value. Use this tool for planning and educational purposes, and consult a financial advisor for specific investment decisions.