Compound interest calculator
Starting capital, a monthly deposit, an annual rate and the years. The calculator compounds month by month and separates what you contributed from what interest generated.
- You will have put in
- €49,000.00
- Earned by interest
- €35,919.32
This is a simulation based on what you typed. It does not replace your books or your advisor.
Take it into your Fider accountHow to use it
- Enter the money you start with, even if it is zero.
- Write the monthly deposit you can genuinely sustain.
- Pick a prudent annual return. 5% is already demanding over the long run.
- Change the years and watch the interest share overtake yours.
How it is calculated
Each month the balance grows by the annual rate divided by twelve and then the deposit comes in. It is the same compounding a periodic contribution plan applies.
What almost nobody does
Compare the same plan starting five years later. With 200 € a month at 5%, those five years of delay cost more than what you contribute in that period.
Inflation and fees
The result is nominal. Subtract expected inflation from the annual rate to see purchasing power, and subtract the product's fees so you do not compound a return you never receive.
Past returns do not guarantee future returns. The result is a projection at the rate you typed.
Frequently asked questions
Does the deposit go in at the start or the end of the month?
At the end, after the month's interest. It is the most common convention and the most conservative.
What return should I use?
It depends on the product. A savings account pays around 2-3%, a global index fund has historically returned 5-7% a year, with no guarantee of repeating it.
Does it account for tax?
No. Capital gains in Spain are taxed when you sell, between 19% and 30% depending on the amount. Pension plans follow different rules.
Can I start with zero?
Yes. The calculator then compounds only the monthly deposits.
Is this the same as the savings simulator?
Same engine. This page is built to share the calculation with a link and explain the result.