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Compound Interest

Simulate your capital growth with periodic contributions and visualize base, contributions and interest separately.

Parameters

Initial capital (€)

5.000 €

Monthly contribution (€)

200 €

Annual rate (%)

Years

15a

Compounding

Annual contribution increase (%)

Final total —

Interest earned —

Initial capital — Base

Total contributed —

Final composition

Base = initial capital · Contributions = monthly deposits · Interest = earnings.

Annual evolution (cumulative)

Base Contributions Interest Total = base+contrib+interest

Year-by-year breakdown

Year	Contributed	Interest	Total	Cum. return

About compound interest

Compound interest is interest on interest — you earn returns on both your initial capital and the accumulated gains. Over years, this creates exponential growth, which is why starting early matters more than the amount.

Formula used

A = P(1+r/n)ⁿᵗ + PMT·[((1+r/n)ⁿᵗ−1)/(r/n)]

P = initial capital, PMT = monthly contribution, r = annual rate, n = compounding per year, t = years.

How to use

Set Initial capital and Monthly contribution
Choose Annual rate and Years
Pick Compounding — Monthly (12×/year) is standard for monthly savers
Set Annual contribution increase if you plan to raise deposits each year

Example

€5,000 initial + €200/month at 7% for 15 years → ~€78,000. You contributed €41,000, interest ~€37,000 (47% of total).

Tips

Start early — time beats amount
Increase PMT yearly to offset inflation
Monthly compounding is most accurate for monthly deposits

FAQ

Monthly vs annual compounding?

Monthly adds interest 12 times a year; annual only once. With monthly contributions, monthly gives the most realistic result.

What is annual contribution increase?

It simulates raising your monthly deposit each year (e.g., 3%). Useful to model salary growth.

Daily compounding?

We approximate it as monthly effective rate — difference vs true daily is <0.1% for typical rates.

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