Free Compound Interest Calculator
See how your investments grow over time with compound interest. 100% in your browser.
How It Works
Calculates how investments grow over time with compound interest and monthly contributions. Enter initial investment, annual rate, period, and monthly additions to see the final amount, total interest earned, and a year-by-year breakdown table. All calculations happen in your browser.
When to Use It
- Planning long-term investments and seeing growth over 5, 10, or 20 years.
- Comparing strategies by adjusting rates and contributions to see wealth impact.
- Demonstrating compound interest power to clients or students with clear tables.
Frequently Asked Questions
Compound vs simple interest?
Simple interest applies only to the original principal. Compound interest applies to principal plus accumulated interest, creating exponential growth — interest on your interest — dramatically increasing returns over time.
How accurate are projections?
Projections assume a constant rate compounded monthly. Real investments fluctuate, so actual returns will vary. Use this to understand compounding power and set targets, but consult a financial advisor.
What monthly contribution matters?
Even small contributions grow significantly with compounding. Try different amounts — the tool shows the impact. A general rule is 10-20% of income, but any consistent amount builds wealth over time.
All calculations happen in your browser. No data is sent to any server.
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