Compound Interest Calculator 2026 – Calculate your investment growth over time
The compound interest calculator calculates your investment value over time when returns are added to principal and continue growing. Enter initial capital, annual return percentage, additional investments, and time to see the final result.
Compound interest or exponential growth is investing's most important principle. The calculator shows capital development annually as a graph, the proportion of original investments, and the return portion. Perfect for retirement saving, ETF investing, and 401k planning.
How does compound interest affect long-term results?
A $10,000 investment with 7% annual return grows to about $38,700 in 20 years — without additional investments. If you add $100 monthly, the result is about $91,000. With a 30-year horizon, $10,000 grows to $76,100 through compound interest alone. The earlier you start, the more time does the work.
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Browse all tools →The compound interest calculator shows how your investments grow through the power of compounding over time. An excellent tool for savers and investors to understand long-term return potential.
Enter initial capital, interest rate, investment period, and possible additional investments – the calculator shows capital growth.
- Calculate compound interest effect over your chosen timeframe.
- Compare how different interest rates and investment amounts affect final results.
- View growth both numerically and graphically year by year.
The calculation assumes steady annual returns, which don't occur in real markets.
- Compound interest effect is especially visible over long time horizons – time is the most important factor.
- Actual returns vary annually – use conservative return assumptions.
- Even small differences in interest rates lead to large differences over long periods.
The calculator doesn't account for taxes, inflation, or investment risks.
- Capital gains taxation reduces actual net returns.
- Inflation eats into nominal returns – subtract inflation to understand real growth.
- Historical returns don't guarantee future performance – investing always involves risks.