Investment & Compound Interest Calculator
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What is an Investment Calculator?
A compound interest calculator shows how an investment grows over time when returns are reinvested — earning returns on both the original principal and accumulated returns. This is the mathematical basis of long-term wealth building. The compound interest formula is A = P(1 + r/n)^(nt), where P is the principal, r is the annual interest rate, n is compounding frequency per year, and t is time in years. Small differences in interest rate or time have dramatic long-term effects: $10,000 invested at 7% for 30 years grows to ~$76,000, but at 8% it grows to ~$100,000. Starting even a few years earlier can double the final value thanks to compounding.
How to Use the Investment Calculator
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Enter your initial investment amount (principal).
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Set the expected annual return rate (e.g. 7% for a diversified stock index fund historical average).
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Enter the investment duration in years.
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Optionally enter a monthly or annual contribution amount if you plan to add regularly.
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Review the chart and yearly breakdown table to see how your investment grows over time.
This investment calculator uses standard compound interest formulas and runs entirely in your browser. It provides a year-by-year breakdown and chart. Useful for retirement planning, savings goal projections, and understanding the long-term impact of different contribution amounts and return rates.
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