Compound interest calculator

What compound interest is

Compound interest means you earn interest on your interest. Save €1,000 at 4% and you have about €1,041 after one year. After two years it is about €1,083, because the second year also earns interest on the first year's interest. The difference looks tiny at first. Over ten or twenty years it becomes the biggest part of your savings — that is why the purple share of the chart grows faster near the end.

How this calculator works

Each month, your balance grows by the monthly share of your yearly rate, matching the compounding you picked (yearly, monthly or daily). Then your monthly amount is added — or taken out — at the end of the month. If you set a yearly increase, the monthly amount changes at the start of each new year: useful when your salary grows, or when withdrawals should keep up with rising prices. The calculator assumes the rate stays the same the whole time, and it ignores fees, tax and inflation. Results are rounded to whole euros.

Everything is calculated in your browser while you type. Nothing you enter is sent to a server, stored, or shared. The "copy link" button is the only thing that puts your numbers in the link, and only when you press it, so you can share the result yourself.

Taking money out instead

Switch to "Taking money out" to answer the opposite question: how long does a pot of money last if you live from it? The balance keeps earning interest while you withdraw, so with a positive rate the money usually lasts longer than simply dividing the total by the monthly amount. With a high enough rate and a steady withdrawal, it may not run out within the chosen years at all.

What rate should I use?

Use a realistic rate, not a hopeful one. For a savings account, use the rate your bank actually pays — it is on the bank's own price list, and it changes over time. For investments, remember that past returns do not promise future ones: markets also go down. When in doubt, run the calculator twice, once with a careful rate and once with an optimistic one, and plan with the careful result.

A quick trick: the rule of 72

Divide 72 by your yearly rate to estimate how many years your money needs to double. At 4%, that is about 18 years; at 6%, about 12. It is an approximation — the calculator shows a closer estimate for your rate under the result.

For many savers, adding a fixed amount every month matters more than small differences in the rate. If you want a simple routine around it, see our monthly money routine.

This calculator is an illustration, not financial advice. Real returns vary and can be negative.