How the Investment Calculator Works
Our investment calculator takes your starting balance (present value), monthly contributions, expected annual return, and time horizon to project your investment's future value. It automatically shows three scenarios: expected return, optimistic, and pessimistic — so you can see the range of possible outcomes based on market variability.
The calculator uses the future value of a series formula: FV = PV × (1+r)^n + PMT × [((1+r)^n − 1)/r]. This formula combines the growth of your initial lump sum with the accumulating growth of your regular contributions. The pessimistic scenario typically assumes a return 50% of the expected rate, while the optimistic scenario assumes 150%.
The Power of Starting Early
Time is the most powerful factor in investing. A 25-year-old investing $500/month at 7% annual return accumulates approximately $1.4 million by age 65. Starting at 35 with the same $500/month yields only $650,000. Starting at 45 yields only $275,000. The difference is compound growth — the extra 10-20 years gives your returns time to earn returns of their own.
A 25-year-old investing $500/month at 7% for 40 years contributes $240,000 of their own money. The remaining $1.1 million is market growth — compound interest doing the heavy lifting. This is why time in the market beats timing the market.
How Contributions Impact Your Outcome
Increasing your monthly contribution has a direct and powerful effect on your final balance. At 7% return over 30 years: $300/month grows to $365,000. $500/month grows to $610,000. $1,000/month grows to $1.22 million. Doubling your contribution doubles your final balance, but the investment return portion stays proportional.
Project Your Investment Growth
Use our free investment calculator to see how your money can grow with different return scenarios and contribution levels.