Compound Interest Calculator
Calculate how your savings evolve over time by applying compound interest to an initial capital plus monthly contributions.
Results
Final capital
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Total contributed
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Interest generated
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The final capital is calculated compounding monthly: initial capital × (1 + r)^n, plus the future value of monthly contributions [(1+r)^n - 1] / r, where r is the monthly interest rate and n the number of months.
Year-by-year evolution
| Año | Saldo final | Aportado acumulado | Interés acumulado |
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When should you use this calculator?
This compound interest calculator helps you project how your savings can grow by combining an initial capital, regular contributions and an estimated return, compounded monthly over the period you choose.
Legal context in Spain
Compound interest is interest where the interest generated in each period is added to the capital and, from that point on, also generates new interest. This causes accelerated capital growth the longer the investment horizon.
The frequency of contributions and compounding affects the final result: the more frequent the contributions and interest compounding, the greater the cumulative effect of compound interest over the long term.
This calculator provides a purely mathematical projection and does not guarantee the actual return of any investment or savings product. Financial markets involve risk and past performance does not guarantee future results; consult a financial advisor before investing.
Frequently asked questions
What is compound interest?
It is interest calculated not only on the initial capital but also on the interest generated in previous periods, causing exponential growth of savings over the long term.
What is the difference between simple and compound interest?
Simple interest is always calculated on the initial capital, while compound interest reinvests the interest generated, which in turn generates new interest. Over the long term, compound interest produces a much larger final capital.
How does contribution frequency affect the result?
The more frequent the contributions (monthly versus annual, for example) and interest compounding, the greater the cumulative effect and therefore the final capital obtained.
What risks does long-term investing carry?
This calculator offers a mathematical projection based on a constant interest rate, but does not guarantee the actual return of any financial product. Markets can fluctuate, so it is worth diversifying and adjusting risk to your time horizon and investor profile.