Calculate how your investments grow over time. Enter your starting principal, monthly contribution, annual return rate, and investment duration to see your projected end balance, total contributions, and total interest earned — with a full year-by-year accumulation breakdown.
Projected End Balance
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Total Contributions
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Total Interest Earned
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Starting Amount
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An investment calculator estimates how much your money will grow over time based on your starting amount, regular contributions, expected annual return, and compounding frequency. It helps you visualize the long-term impact of compound interest so you can set realistic financial goals.
Compound frequency refers to how often your earned interest is added back to your principal and begins earning interest itself. More frequent compounding (e.g. monthly vs. annually) results in slightly higher returns because your interest starts working for you sooner.
A common assumption for a diversified stock market portfolio is 7–10% annually, based on historical S&P 500 averages. More conservative investments like bonds or savings accounts typically yield 2–5%. Use a rate that reflects your actual investment strategy and risk tolerance.
A popular rule of thumb is the 25x rule: multiply your expected annual retirement expenses by 25. For example, if you plan to spend $50,000 per year, you'd aim for a $1.25 million portfolio. This assumes a 4% annual withdrawal rate. Use this calculator to see if your current contributions put you on track.
Yes, though the difference is small. Contributing at the beginning of the month gives your money a few extra weeks of compounding growth each period. Over decades, this can add a meaningful amount to your final balance.
Start by setting a clear goal and timeline, then choose an account type that matches — such as a 401(k) or IRA for retirement, or a brokerage account for general investing. Begin with a diversified, low-cost index fund, automate your monthly contributions, and let compound interest do the heavy lifting over time.
Contributions are the actual dollars you put in — your starting principal plus all your monthly additions. Interest earned (or investment growth) is the money generated by your returns compounding on top of those contributions. In the long run, interest earned can far exceed what you personally invested.
Even a small increase in monthly contributions can significantly boost your end balance over long time horizons thanks to compounding. For example, adding an extra $100 per month over 20 years at 7% return can generate tens of thousands of dollars in additional growth beyond the $24,000 extra you contributed.