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FREE COMPOUND INTEREST CALCULATOR
See how your investment grows with compound interest. Add monthly contributions. Free compound interest calculator with year-by-year breakdown. No signup.
The Power of Compound Interest
Albert Einstein allegedly called compound interest the "eighth wonder of the world". When your interest earns interest, growth becomes exponential over time. $10,000 at 7% annual return becomes $76,123 after 30 years — without adding a single penny. Add $200/month and it becomes $283,385.
Compounding Frequency Matters
- Daily — best but rare in savings accounts
- Monthly — most common for savings and investments
- Quarterly — common for some bonds and CDs
- Annually — least frequent, produces lowest growth
Frequently Asked Questions
What is compound interest?+
Interest calculated on both the principal and the accumulated interest from previous periods. Your interest earns interest, creating exponential growth.
What is a realistic return rate?+
The S&P 500 has averaged about 10% annually before inflation. A diversified portfolio might realistically return 6-8% after inflation over 20+ years.
How does monthly contribution affect growth?+
Monthly contributions dramatically accelerate growth. Even small regular amounts compound significantly over decades.
What is the Rule of 72?+
Divide 72 by your interest rate to estimate how many years it takes to double your money. At 7% per year, money doubles in about 10 years.