Investment Calculator
Project how a starting balance plus regular contributions could grow over time at an expected rate of return.
Formula
About this calculator
An investment calculator projects how money grows when you combine a starting balance, regular contributions, and compounding returns over time. It answers the question every long-term investor asks: if I invest this much now and add this much each month, what could it be worth in 10, 20 or 30 years?
The projection compounds your balance monthly at the expected annual return and adds each contribution at the end of the month. Two forces drive the result: the money you put in (contributions) and the money your money earns (growth). Over short horizons contributions dominate, but as the years pass, compounding takes over — which is why the growth multiple rises the longer you stay invested.
The year-by-year chart separates your cumulative contributions from the total balance, so you can see the exact point where investment earnings begin to outpace what you personally deposit. This crossover is the practical case for starting early: time in the market is the single largest lever most investors control.
Example: starting with $10,000 and adding $500 a month at an 8% annual return grows to roughly $344,000 in 20 years. Of that, $130,000 is your own contributions and the remaining ~$214,000 is investment growth — well over the money you put in. Returns are assumptions, not guarantees, so treat the figure as a planning estimate rather than a promise.
Frequently asked questions
What return rate should I use?
Use a realistic long-run estimate for your asset mix. A broad stock-market portfolio has historically averaged around 7–10% before inflation, but past performance does not guarantee future results, so it is wise to also test a more conservative rate.
How does compounding grow my money?
Each period's returns are added to your balance, so future returns are earned on a larger base. Over long horizons this snowball effect can produce more growth than your contributions themselves.
Does the calculator account for inflation or taxes?
No — it projects nominal, pre-tax growth. To gauge future purchasing power, compare the result against expected inflation, and remember that taxes on gains depend on the account type.
Why start investing early?
The earlier you invest, the more compounding periods your money gets. Starting even a few years sooner can add substantially to the final balance because the earliest dollars compound the longest.
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⚠️ Projections assume a constant rate of return and are for illustration only. Actual investment returns vary, can be negative, and are not guaranteed.