Skip to content
aksoneri

Compound Interest Calculator

See how much an amount can grow when interest is added to itself year after year, and how much of the total comes from what you've contributed.

Result

Currency

The amount you start with.

How much you add each month. Treated as a deposit at the end of the month.

Nominal return, before inflation.

How many years you let the money grow.

Projected Balance

300.851 €

Total Contributions
130.000 €
Growth from InterestAssumption
170.851 €
Value in Today's MoneyAssumption
202.464 €
Real GainAssumption
+55,74 %
Show all years
YearContributionsGrowthBalanceIn Today's Money
116.000 €919 €16.919 €16.587 €
222.000 €2.339 €24.339 €23.393 €
328.000 €4.294 €32.294 €30.432 €
434.000 €6.825 €40.825 €37.716 €
540.000 €9.973 €49.973 €45.262 €
646.000 €13.782 €59.782 €53.084 €
752.000 €18.299 €70.299 €61.200 €
858.000 €23.578 €81.578 €69.626 €
964.000 €29.671 €93.671 €78.380 €
1070.000 €36.639 €106.639 €87.481 €
1176.000 €44.544 €120.544 €96.949 €
1282.000 €53.455 €135.455 €106.805 €
1388.000 €63.443 €151.443 €117.070 €
1494.000 €74.587 €168.587 €127.768 €
15100.000 €86.971 €186.971 €138.922 €
16106.000 €100.683 €206.683 €150.557 €
17112.000 €115.820 €227.820 €162.701 €
18118.000 €132.486 €250.486 €175.380 €
19124.000 €150.790 €274.790 €188.624 €
20130.000 €170.851 €300.851 €202.464 €

How it's calculated

Compound interest means the interest you earn isn't withdrawn — it stays in and starts earning interest of its own. That's why growth looks slow at first and then accelerates.

The calculation here runs month by month. Each month the balance is multiplied by that month's growth factor, then the contribution is added. The annual rate you enter is nominal, so how often interest compounds within the year matters: the same rate produces slightly more when compounded monthly than once a year.

The value in today's money separates nominal growth from real growth. If the balance triples over twenty years but prices also rise, your purchasing power hasn't tripled. That's why the final figure is what really tells you what you can buy.

Example

Starting with €10,000, adding €500 every month, and averaging a 7% return over twenty years, contributions reach €130,000 — but the balance ends up around €300,000. The difference doesn't come from added contributions, but from interest earning interest.

Frequently asked questions

Is 7% a realistic rate?
It's the long-run historical average for a broad stock index, before inflation. It's not a promise: some years are negative and others are far better. Try 4% and 10% too to see how much the result changes.
Why does the result change when I switch compounding?
Because the rate you enter is a nominal annual rate. If interest is added to the balance every month, later months earn interest on top of the interest from earlier months. The more frequently it compounds, the higher the balance at the same rate.
Are taxes and fees included?
No. The result is before capital gains tax and doesn't include fund or platform fees. If you want a picture closer to reality, reduce the return rate by roughly what your annual fees cost.
When is the monthly contribution deposited?
At the end of each month. If you invest at the beginning of the month, each contribution earns one more month of interest, so the actual result will be slightly higher than shown.