Compound Interest (Personal Finance)
Quick Definition
Interest calculated on both the initial principal and accumulated interest from previous periods.
Key Takeaways
- Compound interest works for you in savings and against you in debt
- Starting early dramatically amplifies compounding benefits
- More frequent compounding periods produce slightly higher returns
- The Rule of 72 estimates doubling time: divide 72 by the interest rate
What Is Compound Interest (Personal Finance)?
Compound interest is the mechanism by which interest earns interest over time, causing savings and investments to grow exponentially rather than linearly. In personal finance, understanding compound interest is essential for both growing wealth through savings and investments, and recognizing the true cost of debt. The frequency of compounding (daily, monthly, quarterly, annually) affects the total amount earned or owed. Albert Einstein reportedly called compound interest the eighth wonder of the world, and it remains the most powerful force in long-term wealth building.
Compound Interest (Personal Finance) Example
- 1Investing $5,000 at 7% annual return compounded monthly grows to approximately $10,160 in 10 years without additional contributions.
- 2A credit card balance of $5,000 at 20% APR compounded daily costs over $1,000 in interest annually if only minimum payments are made.
- 3Starting to save $200/month at age 25 vs. 35 can result in over $200,000 more at retirement due to compound interest.
Related Terms
Compound Interest
Interest calculated on both the initial principal and accumulated interest from previous periods, creating exponential growth over time.
Savings Rate
The percentage of income directed toward savings and investments rather than consumption.
Certificate of Deposit (CD)
A time deposit offered by banks that pays a fixed interest rate in exchange for keeping funds deposited for a specific term.
Traditional IRA
A tax-advantaged individual retirement account where contributions may be tax-deductible and earnings grow tax-deferred.
FAFSA (Free Application for Federal Student Aid)
The federal form used to determine eligibility for financial aid including grants, loans, and work-study programs.
401(k)
An employer-sponsored retirement savings plan with tax advantages, often including employer matching contributions.
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