Compound Interest Calculator
Legal Disclaimer: This tool does not constitute financial advice or an investment offer. Calculations are simulations based on historical data that do not guarantee future results.
What is compound interest and how does it work?
Compound interest is the process by which the interest on an investment is reinvested to generate new interest in subsequent periods. Unlike simple interest, where profits are withdrawn, here the capital grows exponentially, creating a multiplier effect over the long term.
The 3 pillars of long-term investing
- Initial Capital (P): The starting amount. While a larger capital speeds up the process, consistency in contributions is often more decisive.
- Rate of Return (r): The annual profit percentage. Small variations in this rate can lead to significant differences in the final capital accumulated after several decades.
- Time Factor (t): The variable with the greatest impact. Compound interest needs years to show its true potential, as the strongest growth occurs in the final stages of the cycle.
*Where A is the total, P the initial, PMT the monthly contribution, i the monthly interest and n the number of months.
The Rule of 72
A simple way to understand the impact of interest is the "Rule of 72". If you divide 72 by your annual rate of return, you will get the approximate number of years it will take for your investment to double without making extra contributions.
Financial Strategy and Concepts
What is the difference between Nominal and Real return?
The nominal return is the gross profit percentage of the investment. The real return is the result of subtracting inflation from that figure. Investing helps capital maintain its purchasing power against the rising cost of living.
Is it better to invest all at once or monthly?
Making periodic contributions (a strategy known as Dollar Cost Averaging) allows you to average the purchase price. This reduces the impact of market volatility and helps generate a disciplined savings habit.
Why do we use values like 10% and 12%?
These figures represent the annualized historical averages of indices like the S&P 500 and the NASDAQ over recent decades. While past returns do not guarantee future profits, they are the most commonly used indicators for realistic financial projections.
How does time affect the final result?
Due to the nature of exponential growth, the earlier the investment process begins, the less effort is needed to reach a financial goal. Time allows accumulated interest to become the main driver of growth.