Free Compound Interest Calculator
Free Investing Tool
Compound Interest Calculator
See how your money grows over time with compound interest and regular contributions. Free, no signup.
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Net Worth Tracker
A Google Sheets dashboard to track your assets, debts and net worth over time — see the compounding happen in real life, month after month.
How compound interest builds wealth
This free compound interest calculator shows how a starting amount plus regular monthly contributions grows over time when your returns compound. Compounding means you earn returns on your past returns — which is why the balance curve gets steeper the longer you leave it.
What is compound interest, simply?
It’s interest on your interest. If you earn 7% on $10,000, next year you earn 7% on $10,700 — not just the original $10,000. Over decades, that snowball effect does most of the heavy lifting, far more than your contributions alone.
Why do monthly contributions matter so much?
Adding even a small amount every month dramatically increases the final balance, because each contribution has years to compound. Try changing the monthly contribution above and watch the interest earned jump.
The most important variable is time
Starting five years earlier often beats contributing more later. To keep the habit going, the Net Worth Tracker lets you log your balances each month and actually see the compounding happen, and the Compound Interest spreadsheet models it year by year.