Zinseszins: Bedeutung, Beispiel und Risiken

Compound interest is interest calculated on an initial principal and on interest accumulated in earlier periods. Once credited interest is added to the balance, later interest calculations use that larger amount. The result depends on the principal, stated interest rate, compounding frequency, time, and the terms of the account, investment, or debt.

Compound interest is a basic concept in saving, investing, and borrowing. Investor.gov defines it as interest paid on principal and accumulated interest. The Consumer Financial Protection Bureau similarly explains it as earning interest on saved money and on the interest earned along the way. This differs from simple interest, which is calculated only on the original principal. Compounding can increase a savings balance over time, but it can also increase an outstanding debt when the agreement provides for interest to be added to the amount owed.

What compound interest means

The principal is the starting amount. At the end of a compounding period, the applicable interest is calculated and added to that amount. The resulting balance becomes the new principal for the next period. Four important inputs are the starting principal, the interest rate, how often interest compounds, and how long compounding continues. Compounding may occur annually, quarterly, monthly, daily, or on another schedule specified by the product or contract. With the same principal, nominal annual rate, and time period, more frequent compounding produces a higher ending balance because interest is added earlier and can itself begin earning interest. This explanation assumes no deposits, withdrawals, fees, payments, or rate changes.

So funktioniert es

Suppose an account begins with $1,000 and pays 5% interest compounded annually. After the first year, 5% of $1,000—or $50—is added, producing a $1,050 balance. In the second year, interest is calculated on $1,050 rather than only on the original deposit. The interest is therefore $52.50, and the new balance is $1,102.50. This repeated recalculation is the defining feature of compound interest. By contrast, simple interest at 5% on the same $1,000 principal would add $50 each year if its other terms remained unchanged. Actual outcomes depend on the governing terms, including the stated rate and the schedule for calculating and crediting interest.

Practical example

Continuing the hypothetical annual-compounding example, the third year’s interest is 5% of $1,102.50, or $55.125. The unrounded balance is therefore $1,157.625, commonly displayed as $1,157.63 when rounded to cents. If the 5% annual rate remained unchanged, no money entered or left the account, and interest compounded once per year, the balance after ten years would be about $1,628.89. This is a mathematical illustration, not a forecast, product offer, or promised return. A real account may have a variable rate, fees, withdrawal rules, or other terms that change the result.

Risks and limitations

Compound interest is a calculation method, not a guarantee of profit or a measure of investment safety. A worked example using a constant rate should not be mistaken for the expected performance of stocks, mutual funds, or other assets whose values can rise or fall. Product and contract terms determine whether interest compounds, the applicable rate, and how often interest is credited or charged. Compounding can also work against a borrower: when a debt agreement adds interest to the amount owed, later interest may be calculated on the increased balance. Consumers should distinguish the nominal rate from the compounding schedule and review the actual terms rather than relying on an illustration.

Frequently asked questions

What is the difference between simple and compound interest?

Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus interest accumulated in earlier periods.

Does compounding frequency matter?

Yes. With the same stated annual rate and other assumptions, more frequent compounding increases the ending balance because credited interest begins earning additional interest sooner.

Can compound interest apply to debt?

Yes. Cornell’s Legal Information Institute describes compounding in connection with both investments and outstanding debt. Whether and how a debt compounds depends on its contract.

Does compound interest guarantee investment growth?

No. Compounding describes how interest is calculated. It does not guarantee a rate, prevent losses, or establish that a financial product is safe.

What can change the result of a compound-interest example?

Rate changes, compounding frequency, deposits, withdrawals, payments, fees, rounding practices, and the amount of time involved can all affect the ending balance.

Educational note: This material explains a market concept; it is not personalized investment advice.

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