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Compound Interest Calculator – Investment Growth Simulator
Visualize how your savings grow over time with compound interest. Enter your starting amount, monthly contribution, expected annual rate, and time horizon. See the final balance, total contributions vs interest earned, and a year-by-year growth table.
How It Works
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1
Enter your numbers
Starting balance, monthly contribution, expected annual return percent, years, and how often interest compounds (monthly, daily, etc.).
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2
See the results
Final balance is shown big at the top. Below: total contributions, total interest earned, and your effective annual return.
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3
Show the growth table
Click Show year-by-year growth to see your starting balance, contributions, interest, and end balance for each year.
Frequently Asked Questions
What rate should I use?
Historical S&P 500 long-term average is around 7-10 percent inflation-adjusted. Conservative bond portfolios: 3-5 percent. High-yield savings accounts: 4-5 percent currently. Use whatever matches your investment vehicle and risk tolerance.
Why does compounding frequency matter?
Daily compounding produces a slightly higher final balance than annual compounding for the same nominal rate. The difference is small but real, visible in the effective annual return display.
Should I invest the lump sum or contribute monthly?
This calculator handles both: a starting amount plus ongoing monthly contributions. Mathematically, lump-sum investing usually beats dollar-cost averaging if the market trends up, but DCA reduces emotional volatility.
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