What is Compound Interest?
Compound interest is the interest calculated on the initial principal and also on the accumulated interest of previous periods. It's often called "interest on interest" and can cause wealth to grow exponentially over time.
The power of compound interest is considered one of the most important concepts in finance. Albert Einstein reportedly called it the "eighth wonder of the world" and "the most powerful force in the universe."
How is Compound Interest Calculated?
Compound interest is calculated using the standard compound interest formula, which accounts for your initial investment, regular contributions, the interest rate, compounding frequency, and the time period of your investment.
Where:
- A = Future value of the investment
- P = Principal investment amount
- r = Annual interest rate (decimal)
- n = Number of times interest is compounded per year
- t = Number of years the money is invested
- C = Regular contribution amount
This calculator allows you to adjust all these variables to see how they impact your investment growth.
The Power of Compound Interest
Time is Your Greatest Asset
The longer your money compounds, the more dramatic the growth. Starting early with regular investments can create substantial wealth over decades, even with modest contributions.
Frequency Matters
The more frequently interest is compounded, the faster your money grows. Daily compounding will yield slightly more than monthly, which yields more than annual compounding.
Consistent Contributions Amplify Growth
Regular contributions, even if small, can have a significant impact on your investment growth over time. Setting up automatic investments can help maintain consistency.
The Rule of 72
A quick way to estimate how long it will take for an investment to double is using the Rule of 72: Divide 72 by your annual interest rate. For example, at 7% interest, your money will double in approximately 10.3 years (72 ÷ 7 = 10.3).