Compound Interest Calculator

Compound interest is interest earned on your interest. As your investment grows, each year's return is calculated not just on your original money but on all the returns already added. Over time this snowballs - which is why starting early matters so much and why Einstein reportedly called it the eighth wonder of the world.

With regular monthly contributions the future value is: Principal × (1 + r)^n + Contribution × ((1 + r)^n − 1) ÷ r, where r is the monthly rate and n the number of months. This calculator does it month by month, so the growth chart reflects real monthly compounding rather than a rough annual estimate.

Because every contribution starts compounding immediately. In the chart you can watch the gold "interest earned" block overtake the "contributions" block - often somewhere between years 15 and 25. After that crossover, your money is doing more of the work than you are, which is the whole goal of long-term investing.

Nominal is the headline number; real subtracts inflation to show your actual purchasing power. A pot of 1,000,000 in 25 years sounds huge, but if inflation runs high it might buy far less than today. Enter an inflation rate and the tool shows the real (inflation-adjusted) value too - the number that actually matters.

More frequent compounding (monthly or daily) slightly beats annual, because interest starts earning sooner. This calculator uses monthly compounding, a good match for most funds and investment accounts. The bigger levers, though, are your rate, your contributions and - above all - time.

Yes. Alvest tracks the real compound growth of your actual portfolio - across stocks, funds, gold and crypto - and projects it forward with your contributions and goals, in real (inflation-adjusted) terms. You can start free.