Project how an investment could grow over time, based on your starting amount, regular contributions, and expected return.
This calculator compounds your starting balance and each monthly contribution forward using your expected annual return, applied monthly. Your initial amount compounds for the full period, while each new contribution starts compounding from the month it's added — so contributions made early in the timeline have more time to grow than ones made near the end.
Small differences in expected return compound into large differences over long periods. A portfolio returning 5% versus 8% annually can produce a dramatically different final balance over 20-30 years, even with identical contributions — which is why it's worth using a conservative, realistic estimate rather than an optimistic best case.
| Return assumption | Typical use |
|---|---|
| 3–4% | Conservative, bond-heavy portfolio |
| 6–7% | Balanced stock/bond portfolio (long-term average) |
| 8–10% | Aggressive, stock-heavy portfolio |
Treat the result as a planning estimate, not a guarantee — past returns don't predict future performance.
Enter your starting investment amount, how much you plan to contribute regularly (monthly), your expected annual return rate, and the number of years you plan to invest. Click Calculate, and the tool projects your investment's growth over time, showing how your balance compounds as both your contributions and their accumulated returns build on each other year after year.
Compound growth means your returns start generating their own returns, which is why the growth curve of an investment accelerates the longer money stays invested — the effect is relatively modest in the early years but becomes substantial over decades. A $10,000 investment growing at 7% annually roughly doubles every 10 years due to compounding alone, without any additional contributions. This is why starting to invest earlier, even with smaller amounts, often outperforms starting later with larger amounts, simply because the earlier money has more time for compounding to work.
It's tempting to project using an optimistic return rate, but doing so can lead to significantly overestimating how much an investment will actually be worth. Historical long-term stock market averages (accounting for inflation) tend to fall somewhere in the 6-7% range annually for diversified portfolios, though any single year can vary dramatically above or below that average. Using a conservative, realistic return assumption for planning purposes — rather than the best year on record — tends to produce projections that are less likely to leave you short of a financial goal if actual returns come in lower than hoped.
Regularly adding to an investment — sometimes called dollar-cost averaging — has a different growth pattern than investing a single lump sum up front. A lump sum invested early has the maximum possible time to compound, generally outperforming an equivalent total amount spread out as smaller contributions over time, assuming markets trend upward over the long run. That said, regular contributions are often more realistic for most people, since they align with how income is actually earned (paycheck by paycheck) rather than requiring a large sum to be available all at once, and consistent contributions also reduce the risk of poor timing by spreading purchases across different market conditions.
This projection assumes a smooth, constant annual return applied consistently every period, but real markets don't behave this way — actual returns fluctuate significantly year to year, sometimes dramatically, even if the long-term average matches the assumed rate. This tool also doesn't account for taxes on investment gains, which vary based on account type (taxable brokerage vs. tax-advantaged retirement accounts) and how long investments are held. Investment fees, fund expense ratios, and inflation eroding purchasing power over time are similarly not factored in, all of which mean the actual real-world value of an investment may differ meaningfully from this simplified projection.
Why does my investment grow slowly at first, then faster later? This reflects compounding — early on, most of the balance comes from your own contributions, but as accumulated returns grow larger, they begin generating meaningful additional growth on their own, accelerating the overall curve.
Should I use a higher return assumption if I'm investing in stocks vs. bonds? Generally yes, since stocks have historically produced higher average long-term returns than bonds, though with correspondingly higher year-to-year volatility — adjust your assumed rate to reflect your actual portfolio allocation.
Does inflation affect this projection? Not directly — the projected balance is in nominal (non-inflation-adjusted) dollars. To estimate purchasing power in today's terms, you'd need to separately reduce the projected figure by an assumed inflation rate over the same period.
Is a more aggressive contribution schedule always better? Contributing more, when financially feasible, generally accelerates growth, but sustainable, consistent contributions over a long period usually outperform an aggressive but inconsistent approach that gets interrupted by financial strain.
How does this differ from a compound interest calculator? They use similar underlying math, but this tool is framed specifically around investment growth with regular contributions, which is the typical pattern for retirement or brokerage account planning.
What return rate should I use for a diversified stock portfolio? Historical long-term averages vary by market and time period — using a conservative, well-researched figure rather than an optimistic recent-years average tends to produce a more realistic long-term projection.
Does this calculator work for retirement accounts specifically? The math applies to any regularly contributed, compounding investment account, including retirement accounts, though tax treatment differs by account type and isn't factored into this projection.
How does dollar-cost averaging relate to this calculator? Regular monthly contributions, as modeled here, are a form of dollar-cost averaging — investing a fixed amount consistently over time regardless of market conditions, which smooths out the effect of price volatility.
Last reviewed by Mehmed on July 11, 2026.