Compound Interest Calculator
See how your money can grow. Enter a starting amount, monthly contributions and an expected return — the calculator projects your balance year by year, with interest compounding on your chosen schedule.
Your plan
Projection
Year-by-year growth
| Year | Balance | Interest earned |
|---|
Why Compound Interest Is So Powerful
Compound interest means you earn returns on your returns — not just on what you put in. That’s why the bar above shifts: early on, your contributions do most of the work, but over decades the interest becomes the bigger slice. Starting ten years earlier often beats contributing twice as much later. Time in the market is the real multiplier.
What Return Should You Expect?
There’s no guaranteed number. The U.S. stock market has averaged roughly 7–10% per year over very long periods before inflation, while savings accounts and bonds pay far less with far less volatility. Use this calculator to test scenarios — try 5%, 7%, and 9% to see how sensitive your plan is to the return assumption, and never invest money you’ll need soon in volatile assets.
Frequently Asked Questions
What’s the difference between compound and simple interest?
Simple interest pays only on your original principal. Compound interest pays on principal plus accumulated interest, so growth accelerates over time.
Does compounding frequency matter much?
A little — daily compounding beats annual compounding at the same rate, but the difference is small compared to your contribution amount, return rate, and time horizon. Focus on those first.
Are these projections guaranteed?
No. This is a math projection, not financial advice. Real investments fluctuate, fees eat into returns, and taxes apply. Use it for planning, not promises.