Limiar Finance

This calculator is for educational purposes only and does not constitute financial advice. Consult a certified professional before making investment decisions.

Compound Interest Calculator

Calculate the growth of your investment with compound interest

Equivalent monthly rate: 0.9489% a.m.

The Power of Compound Interest

Compound interest is the mechanism by which an investment earns returns not only on the original principal, but also on the accumulated interest over time. It is often called “interest on interest” — and the compounding effect over long periods is remarkably powerful. The earlier you start investing, the more time your capital has to grow exponentially.

How the Formula Works

The classic compound interest formula is A = P × (1 + r)ⁿ, where A is the final amount, P is the initial principal, r is the interest rate per period, and n is the number of periods. When you add regular monthly contributions, each deposit also starts earning compound interest from the month it is invested, further accelerating portfolio growth.

This calculator converts the annual rate you enter into the correct monthly equivalent using the formula: r_monthly = (1 + r_annual)^(1/12) − 1. This conversion is more accurate than simply dividing by 12, which underestimates the true return and can produce significant distortions over long investment horizons.

The Role of Monthly Contributions

Regular monthly contributions are the single most powerful wealth-building tool available to everyday investors. The consistency of contributions matters more than the size of each individual deposit. A monthly contribution of R$ 500 at 12% per year over 20 years results in approximately R$ 494,000 — of which more than R$ 374,000 comes entirely from compound interest. The directly invested capital represents only 24% of the final amount; the remaining 76% was generated by time and the power of reinvestment.

For Brazilians living abroad who maintain savings in reais back in Brazil, this calculator helps visualize the growth of fixed-income investments, funds, and equities over time — making it easier to plan toward goals like retirement, real estate purchase, or building an emergency fund.

How to Use This Calculator

For accurate and useful simulations, follow these guidelines:

  • Initial capital: the amount you have available to invest today. This can be zero if you are starting from scratch with monthly contributions.
  • Monthly contribution: the amount you plan to invest regularly each month. Use realistic figures to obtain meaningful projections.
  • Annual rate: enter the gross annual rate of your investment — the calculator automatically converts it to the correct monthly equivalent.
  • Period: your investment horizon in months. For 5 years, enter 60; for 10 years, 120; for 30 years, 360.

Compare different scenarios by adjusting the investment period to see the impact of time on the final portfolio value. The results from this calculator are estimates for educational purposes and do not account for inflation, taxes, or rate changes.