Compound Interest Calculator

Compound interest is one of the most important forces in long-term investing because returns are applied not only to your original principal, but also to previously earned returns. This calculator helps you model that effect in a practical way by combining your starting balance, recurring monthly contributions, projected annual rate of return, compounding schedule, and a total time horizon in years. The result is a clear estimate of how much of your ending value comes from direct contributions versus accumulated interest.

The tool converts your annual rate into a periodic rate based on your selected compounding frequency. For example, monthly compounding applies interest 12 times per year, while daily compounding applies interest 365 times. At each period, the model applies growth to your current balance and then adds a proportional share of your monthly contribution. Repeating this cycle over your entire horizon creates a realistic projection curve that highlights how returns accelerate over time. The year-by-year table is useful for reviewing milestones, while the chart helps you compare the steady baseline from contributions against the widening gap created by interest.

This projection is designed for planning, not for guaranteed outcomes. Real portfolios experience volatility, taxes, and fees, and those factors can alter long-term performance. Still, using a consistent framework makes it easier to test scenarios such as increasing monthly deposits, extending your timeline, or adjusting expectations for annual return. Quik-Calc provides this calculator so you can make more informed financial decisions with transparent, easy-to-interpret assumptions.

Keep in mind that this calculator uses a fixed annual rate of return and does not account for inflation, market downturns, or taxes on investment gains. Actual investment returns will vary, sometimes significantly. Before making any investment decisions, consider speaking with a qualified financial advisor who can assess your personal situation, risk tolerance, and time horizon. This tool is free to use and intended for educational purposes only.