Compound Interest Calculator
Calculate how your investments grow with compound interest. See the power of long-term investing.
Investment Growth
Compound Interest Guide
What is Compound Interest?
Compound interest is interest earned on both your principal investment and the interest already accumulated. This creates exponential growth over time, often called "interest on interest." The more frequently interest compounds, the faster your money grows.
Simple vs Compound Interest
Simple Interest: Calculated only on the principal amount. Formula: I = P × r × t
Compound Interest: Calculated on principal plus accumulated interest. Formula: A = P(1 + r/n)^(nt)
Compounding Frequencies Explained
- Daily: Interest calculated 365 times per year (fastest growth)
- Monthly: Interest calculated 12 times per year
- Quarterly: Interest calculated 4 times per year
- Annually: Interest calculated once per year (slowest growth)
The Power of Time: Rule of 72
The Rule of 72 is a quick way to estimate how long it takes for your investment to double. Divide 72 by your annual interest rate. For example, at 8% interest, your money doubles in approximately 72/8 = 9 years. This shows why starting early is crucial for wealth building.
Investment Tips
- Start investing early to maximize compound growth
- Choose investments with higher interest rates when possible
- Reinvest earnings to accelerate compound growth
- Avoid withdrawing money before maturity
- Consider tax implications on investment returns
Frequently Asked Questions
Why is compound interest better than simple interest?▼
Compound interest grows exponentially because you earn interest on your interest. Over time, this creates significantly higher returns than simple interest, which only earns on the principal.
What's the best compounding frequency?▼
Daily compounding produces the highest returns, followed by monthly, quarterly, and annual. However, the difference becomes smaller with higher interest rates. Always choose the highest compounding frequency available.
How long does it take to double my investment?▼
Use the Rule of 72: Divide 72 by your interest rate. At 8%, it takes 9 years to double. At 10%, it takes 7.2 years. This shows the power of higher returns over time.
Should I reinvest my earnings?▼
Yes! Reinvesting earnings accelerates compound growth significantly. This is why long-term investments in retirement accounts (like retirement annuities) are so powerful.
Understanding Compound Interest
Compound interest is interest earned on both your principal and previously earned interest. The more frequently interest is compounded, the more you earn.
Formula: A = P(1 + r/n)^(nt), where A is the final amount, P is principal, r is rate, n is compounding frequency, and t is time in years.