Investment Calculator
See how compound interest grows your investments over time. Enter your initial investment, monthly contributions, expected return rate, and time horizon.
Investment Details
Projected Growth
Growth Over Time
The Power of Compound Interest
Compound interest is often called the "eighth wonder of the world." Unlike simple interest, which only earns returns on your initial investment, compound interest earns returns on both your principal AND your accumulated interest. This creates an exponential growth curve that accelerates over time.
How the Investment Calculator Works
This calculator uses the compound interest formula with monthly compounding: FV = PV(1+r)^n + PMT[((1+r)^n - 1)/r], where PV is your initial investment, r is the monthly interest rate, n is the number of months, and PMT is your monthly contribution. The result shows your projected portfolio value at the end of your investment period.
Investment Tips for Beginners
Start early — even small amounts grow significantly over decades. The S&P 500 has historically returned about 10% annually before inflation. Diversify across asset classes, keep fees low with index funds, and stay consistent with monthly contributions regardless of market conditions.
Key Facts
- 01S&P 500 avg return: ~10%/year
- 02Rule of 72: divide 72 by rate to find doubling time
- 03Starting 10 years earlier can double your returns
- 04Index funds typically charge 0.03-0.20% fees