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Compound interest calculator

See how much your money can grow by investing consistently.

The money you start with today, before any contributions.
How much you add on each periodic contribution (based on the chosen frequency).
How often you add money. Contributing more often puts your money to work sooner; it does not change how often interest is compounded.
How often interest is credited and starts earning interest itself. It is independent of the contribution frequency: with annual compounding the return is the effective annual return; with monthly, the annual rate is split into 12 (a nominal rate, like a TIN) and earns slightly more. With a contribution of 0 the result depends only on this option.
The average annual return you expect. With annual compounding it is the effective annual return; otherwise it is read as a nominal annual rate. Global stocks have historically returned around 7% nominal, but it is not guaranteed.
How many years you stay invested. Time is the most powerful factor in compound interest.
Annual product costs (a fund/ETF TER). They subtract from your net return. An index fund is usually around 0.1-0.4%.
If you raise your contribution each year (with inflation or salary), enter it here. Leave at 0 if fixed.
If set, you will see the final value in today purchasing power. Leave at 0 to reason in nominal euros.
Final value
€262,050
Total contributed
€95,000
Interest earned
€167,050

Investment growth

Show the chart data: Investment growth

Final value composition

Final value€262,050
  • Contributed€95,00036%
  • Interest€167,05064%

Information, not tax or financial advice.

How the compound interest calculator works

This calculator projects how much your investment could be worth by combining three forces: the initial capital, the regular contributions and the annual return that gets reinvested. There are two different frequencies: the contribution frequency (how often you add money) and the interest compounding (how often interest is credited and starts earning interest itself).

How to read the result. The final value splits into what you put in (total contributed) and what the money generated on its own (interest earned). Over the long run, that second part usually ends up the larger.

Worked example (default values). You start with €5,000, add €300 a month at 7 % annually for 25 years, with annual compounding (the default option):

  • Total contributed: €5,000 + (€300 × 12 × 25) = €95,000.
  • Estimated final value: about €262,050.
  • Interest earned: about €167,050, nearly double what you contributed.

Contribution frequency vs. compounding. The contribution frequency only decides when your money goes in (at the end of each period): with a contribution of 0, changing it does not alter the result. Compounding does: with annual, the percentage is the effective annual return (€10,000 at 7 % is €10,700 after a year); with monthly, the percentage is a nominal rate split by 12 (like a TIN), so €10,000 at 7 % becomes €10,722.90. With the example above and monthly compounding the final value would be about €271,649. If your product quotes a TAE (APR/APY), use annual compounding; if it quotes a TIN credited monthly, use monthly.

An important note. The return is an estimate, not a guarantee. To think in real purchasing power, subtract inflation (7 % nominal − 3 % ≈ 4 % real).

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