Calculate compound interest growth on an investment, including regular monthly contributions, with a full breakdown of principal vs. interest earned.
Compound interest is interest calculated on both the initial principal and accumulated interest from previous periods, causing growth to accelerate over time versus simple interest.
More frequent compounding (daily or monthly vs. annually) produces slightly higher returns, since interest is calculated and added more often.
Yes, this calculator adds your regular monthly contribution on top of compound growth from your initial principal.
It's similar in concept — regular contributions compounding over time — though a dedicated SIP calculator may use fund-specific assumptions. This tool uses a standard fixed-rate compound growth model.
Compound interest is often called one of the most powerful forces in personal finance, because it causes money to grow at an accelerating rate over time — interest earns interest, which earns more interest, compounding on itself. This calculator computes exactly how a lump-sum investment (with optional ongoing monthly contributions) grows over time at a given interest rate and compounding frequency.
The basic compound interest formula for a lump sum is A = P(1 + r/n)^(nt), where P is the principal, r is the annual interest rate, n is the number of times interest compounds per year, and t is the number of years. When regular contributions are added, this calculator also computes the future value of that contribution stream using the standard future-value-of-annuity formula, then adds both together for the total future value.
The same annual interest rate produces slightly different results depending on how often it compounds. Daily compounding produces marginally higher returns than monthly, which in turn produces higher returns than annual compounding, because interest gets added to the principal more frequently, giving it more opportunities to itself earn interest within the same year. The difference is usually small for typical rates and timeframes, but it grows more noticeable over longer periods or at higher interest rates.
Adding a modest recurring contribution to an initial lump sum can dramatically change the final outcome over a long time horizon. This is because each new contribution starts compounding from the moment it's added, so contributions made early in the investment period have much longer to grow than contributions made near the end. This calculator's breakdown separates how much of your final total came from your original principal plus contributions, versus how much came purely from interest earned — a useful way to see compounding's effect concretely.
All calculations run directly in your browser — your financial details are never sent to a server or stored anywhere.