Project how an initial investment plus regular monthly contributions could grow over time at a given rate of return.
8% a year is a commonly used long-run average for a diversified stock portfolio before inflation. Actual returns vary year to year.
This tool projects the future value of an initial lump sum plus regular monthly contributions, using the standard compound growth formula applied monthly. It combines two growth sources: the compounding of your initial investment, and the compounding of every future monthly contribution from the month it's made until the end of your time horizon.
If you only want to project a single lump sum with no ongoing contributions, our Compound Interest Calculator is a simpler tool built for exactly that case.
Starting with $10,000 and adding $200 a month for 20 years at an assumed 8% average annual return, you would contribute $58,000 out of pocket over that time. With compounding, that grows to a projected portfolio value of approximately $167,072 - meaning roughly $109,072 of that final total comes purely from investment growth, not from money put in directly.
How accurate is this investment calculator?
It's a planning estimate, not a guarantee. It assumes the same annual return every single year, but real markets fluctuate - some years will beat your assumed rate, others will lose money. Over long periods the average tends to smooth out, but your actual balance at any given date will differ from a straight-line projection.
What rate of return should I use?
A commonly cited long-run average for a diversified U.S. stock portfolio is around 8-10% per year before inflation, or roughly 6-7% after inflation. A more conservative mixed stock-and-bond portfolio might use a lower assumption, like 5-6%. Try a couple of different rates to see a range of outcomes.
Does this include taxes or investment fees?
No - this is a gross growth projection before any taxes on gains or account/fund fees. Fees and taxes can meaningfully reduce your actual return over decades, so treat this as an upper-bound estimate rather than a guaranteed take-home figure.
What's the difference between this and a retirement calculator?
The math is the same, but our Retirement Calculator is framed specifically around your current age, target retirement age, and an optional employer 401(k) match. This tool is for any general investment goal with a chosen time horizon, not tied to retirement specifically.
Does this account for inflation?
Not directly - it shows the raw dollar amount your investment could reach. If you enter a return rate that's already adjusted for inflation (a "real" return), the projected total is a rough estimate in today's purchasing power; if you use a nominal rate, the number will be larger but buy less by the end of your time horizon.
Should I invest a lump sum or contribute monthly?
Both work with this calculator - set the monthly contribution to 0 if you only want to project a one-time investment, or increase it to see how ongoing contributions add to your total. Many investors do both: an initial deposit followed by regular contributions.
What counts as a good annual return?
Historically, broad U.S. stock market indexes have averaged high single digits to low double digits annually over long periods, though any individual year can vary enormously, including significant losses. Bonds and cash historically return less but with lower volatility.
Can I use this for retirement accounts like a 401(k) or IRA?
Yes - the math works the same way regardless of account type. If your employer offers a matching contribution, our Retirement Calculator specifically accounts for that match; this tool assumes all contributions come from you.