Investment Calculator
Project how a portfolio could grow with regular contributions and an assumed average annual return.
Understanding the Investment Calculator
This calculator projects portfolio growth the same way a compound interest calculation works, but it’s framed around investing assumptions: a starting balance, a steady monthly contribution, and an average annual return you expect the portfolio to earn over the long run — commonly modeled between 5% and 10% for diversified stock portfolios, though actual returns vary significantly year to year.
The gap between “total contributed” and “future value” is your projected investment gain — money the market added on top of what you put in. That gap tends to be small in the early years and large in later ones, because most of it comes from years of compounding on gains that are themselves compounding.
Markets don’t move in a straight line. A single average-return assumption smooths over real volatility, so use this for long-range planning and goal-setting, not as a prediction of any specific year’s performance.
See it in practice
Example 1 — Long-horizon investing plan
Example 2 — Shorter horizon, higher contribution
Common questions
There’s no single right answer — it depends on your asset allocation and risk tolerance. Many long-range planning tools use a range like 5–8% for a diversified stock-heavy portfolio; run the calculator at a few different rates to see a range of outcomes rather than one number.
No. Fund expense ratios, advisory fees, and taxes on gains or dividends will all reduce real returns below the rate you enter — treat the output as a gross, pre-cost projection.
No — set it to 0 to project a lump sum with no further investing, which turns this into the same math as the compound interest calculator.
This tool projects a portfolio’s growth in isolation. The retirement calculator adds a retirement-specific lens, like estimating sustainable withdrawal income from the resulting balance.
A commonly cited long-run historical average for a diversified U.S. stock portfolio falls between 7% and 10% annually before fees and taxes. Any single year can vary well above or below that range, so a more conservative assumption is often prudent.
Historical data generally favors investing a lump sum immediately over spreading it out, since markets have risen more often than they’ve fallen. Dollar-cost averaging is more valuable for money you’re earning gradually, like a paycheck.
The required amount depends heavily on your time horizon and assumed return. At an 8% average annual return, roughly $500 a month for 35 years, or roughly $1,700 a month for 20 years, would each get you to around $1.1 million.
No, many brokerages and index funds allow you to start with small amounts, sometimes even a few dollars. Starting early and contributing consistently generally matters more than the size of your initial investment.
Saving typically means keeping money in a low-risk, easily accessible account like a savings account. Investing means putting money into assets like stocks or bonds that carry more risk but have historically offered higher long-term returns.
Checking once or twice a year is generally enough for a long-term investor, since frequent checking during market volatility can encourage emotional decisions like selling during a downturn, which historically hurts long-run returns.
No, investment returns are never guaranteed, and projections based on historical averages are estimates, not promises. Actual returns depend on market performance, fees, and the specific investments held.