// INVESTING
Compound Interest Calculator
Use this free compound interest calculator to see how your money grows over time. Enter your starting amount, monthly contributions and interest rate.
$
$
%
—
Final Value
—
Total Contributed
—
Interest Earned
—
Money Multiplied
How to use this compound interest calculator
Enter your starting amount, how much you will add each month, your expected yearly return and how many years you will invest. The compound interest calculator shows your final balance, how much you put in and how much came from interest.
For long-term stock market investing, many people use 5% to 7% a year as a cautious assumption; savings accounts usually pay less. Returns are never guaranteed. The SEC's Investor.gov explains compound interest and investing basics in more detail.
Frequently Asked Questions
What is compound interest?
Compound interest means you earn interest on your interest — not just on your original deposit. Over time, this snowball effect is the most powerful force in personal finance. Einstein reportedly called it the eighth wonder of the world.
What is a realistic investment return to use?
The S&P 500 has historically returned about 7–10% annually (inflation-adjusted: ~7%). For conservative planning, use 6–7%. For a high-growth scenario, use 9–10%. Do not use more than 10% — markets do not guarantee returns.
How much should I invest each month?
A common target is 15% of your gross income. If you cannot hit that, start with whatever you can — even $50/month at 8% over 30 years becomes over $74,000. The key is to start early and stay consistent.