Estimate how an investment portfolio grows over time with regular contributions and compounding returns. Adjust the numbers below to see your future value instantly.
This investment growth calculator turns four simple inputs — your initial investment, your monthly contribution, an expected annual return and a time horizon — into a full portfolio projection. Instead of guessing where a brokerage or index-fund account might land in a decade or two, you get a concrete future value, a clear split between the money you contributed and the money the market added, and an optional year-by-year table that shows the balance climbing one row at a time. It is built for people who invest regularly and want to see where a steady habit could lead.
Because the tool is framed around a growing portfolio rather than a one-off deposit, it is most useful for long-term investing goals: building wealth through index funds, dollar-cost averaging into the market every payday, or stress-testing whether your current pace is enough. If your question is narrower — how fast a single sum doubles, for example — the Rule of 72 calculator gives a one-line answer, and the future value calculator isolates a lump sum with no recurring investing.
Every projection on this page is powered by two engines pulling in the same direction. The first is your contributions: the initial investment plus every monthly deposit you make. This part of the balance is fully within your control and is the dominant force in the early years. The second engine is compounding returns — the gains your invested dollars earn, reinvested so that those gains start earning gains of their own. Early on, contributions do most of the heavy lifting. Given enough time, the second engine overtakes the first, and growth from the market can exceed everything you ever deposited.
Here P is your starting investment, PMT is each monthly contribution, r is the periodic return rate, and n is the number of periods. The calculator applies this monthly, dividing your annual return by twelve and running the loop month by month, which mirrors how real investment accounts credit growth and produces a more accurate figure than a once-a-year calculation. The underlying mathematics is the same compounding engine explained on the compound interest calculator, which layers on tax and inflation controls if you want purchasing-power numbers.
The expected return is the single input that most influences your projection, and it is also the one people get wrong most often. A diversified, stock-heavy portfolio has historically delivered something in the region of 6 to 7 percent a year after inflation over long stretches, though individual decades have ranged from spectacular to disappointing. A more balanced portfolio that blends bonds with equities will usually project lower, perhaps 4 to 5 percent, in exchange for a smoother ride.
The honest way to use this field is not to pick one optimistic number and admire the result. Run the calculator three times: a cautious rate, a middle-of-the-road rate, and a hopeful one. The spread between those three ending balances is your real range of outcomes. If your plan only works at the top of that range, it is fragile; if it works even at the bottom, it is robust. Because returns arrive unevenly in real life rather than as the smooth average the formula assumes, treating the projection as a band rather than a point is the more truthful reading.
The default fields assume a fixed monthly contribution, but in reality most investors can afford to invest a little more each year as their income rises. This matters more than it first appears. A dollar invested in year one of a thirty-year projection compounds for the full three decades, so the contributions you make early are worth far more at the finish line than the ones you make near the end. Front-loading your investing — or simply nudging the monthly amount up whenever you get a raise — is one of the highest-leverage moves available to a long-term investor.
To see this for yourself, set a baseline projection, then raise the monthly contribution by even ten or twenty percent and recalculate. The gap between the two ending balances is usually far larger than the extra you put in, because every additional dollar buys years of compounding. This is also why starting early beats trying to catch up later: time, not timing, is the investor's biggest advantage.
Imagine three people who each start with $10,000 and assume a 7 percent annual return over 25 years. That 7 percent is an illustrative assumption, not a promise — actual returns vary year to year and past performance does not guarantee future results. Avery invests nothing more and simply lets the lump sum ride. Blair adds $300 a month. Casey adds $600 a month. Avery's balance grows purely through compounding, roughly five-fold, which is impressive on its own. Blair's steady $300 monthly deposits, however, push the ending balance well past Avery's, because the recurring contributions keep feeding the compounding engine. Casey, contributing double, ends up with dramatically more — not twice Blair's growth, but more, because the larger early contributions compound the longest.
The lesson is not the exact dollar figures, which you can reproduce in the calculator above, but the shape of the outcome: consistent monthly investing reshapes a projection far more than a single starting deposit. Enter your own numbers to see where your habits would place you among the three.
Switch on the year-by-year breakdown and a useful pattern emerges. In the first few rows, the “contributed” column dwarfs the “growth” column — you are mostly looking at your own money. Somewhere in the middle of a long projection the two columns cross over, and from that point growth becomes the larger share of each year's gain. That crossover point is the moment compounding takes the wheel, and reaching it is the entire reason long-term investing rewards patience.
Use the table to set expectations rather than to obsess over any single year. Markets do not climb in a straight line, so your real account will sit above the projected line in good years and below it in bad ones. The table shows the trend the average is pointing toward, which is exactly what you need for planning even though the path will be bumpier.
A 7 percent average does not mean 7 percent every year. Sequence risk — the order in which good and bad years arrive — can meaningfully change real outcomes, especially once you start withdrawing. Treat the projection as a planning aid, not a promise.
A one percent annual fee quietly subtracts from your real return every year. If your funds carry costs, model a slightly lower rate to account for them. For after-tax figures, the compound interest calculator lets you apply a tax rate directly. Investors planning for a specific retirement date should also compare this projection with the retirement calculator, which frames the same growth around a target retirement age, and the FIRE calculator, which shows how a high savings rate can pull financial independence forward by years.
Money you will need within a few years usually does not belong in a volatile portfolio. For short-term targets and emergency funds, the savings growth calculator uses a steadier APY model that better reflects how a high-yield savings account behaves.
Understand the ideas behind the projection. These guides explain the mechanics this calculator puts to work — read the full library in the Learn hub.
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