How to use this investment growth calculator
Use the single-scenario mode when you want to project one set of investment assumptions. Enter your starting investment, planned monthly contribution, expected annual return, investment horizon, and any annual contribution increase you want to include.
Treat the expected annual return as a planning assumption rather than a prediction. It can be useful to test more conservative and more optimistic return assumptions to understand how sensitive a long-term projection may be to the rate you choose.
The annual contribution increase lets you explore a plan in which your regular contribution grows over time rather than remaining fixed. This can be useful if you expect to raise the amount you invest as your income or savings capacity increases.
Use comparison mode when you want to evaluate two different investment plans from the same starting investment. Scenario A and Scenario B can use different monthly contributions, annual return assumptions, investment horizons, and annual contribution increases.
Understanding your results
Ending value is the projected value of the investment at the end of the selected horizon under the assumptions you entered. It reflects the money you contribute as well as the modeled investment growth associated with your assumed return.
Total money contributed helps separate the amount coming from your own deposits from the portion of the projection attributed to investment performance. If you use an annual contribution increase, total contributions can rise substantially over a long horizon because your planned contribution amount also increases.
Modeled investment growth is the portion of the projected ending value attributable to the assumed investment return rather than your contributions. This number is hypothetical because actual market returns can be higher, lower, or negative.
Ending monthly contribution shows the recurring contribution level reached by the end of the projection when an annual contribution increase is included. It can help you judge whether a savings plan that looks attractive mathematically also seems realistic for your future budget.
In comparison mode, the calculator also helps explain the difference between the two projected ending values. Rather than showing only which scenario finishes with more money, it distinguishes the effect of different contribution amounts from the difference associated with modeled investment growth.
What can affect your investment growth estimate
Your monthly contribution
Regular contributions can be a major driver of long-term investment value. Increasing the amount you invest each month generally raises both the amount of your own money in the account and the amount of capital that has the opportunity to earn future returns.
For many investors, contribution decisions are also more directly controllable than market returns. Comparing different monthly contribution levels can therefore be useful when deciding how much of a long-term goal depends on saving more versus assuming stronger investment performance.
Your assumed annual return
A higher return assumption produces a larger projected value, especially over longer periods. That does not mean the higher rate is more likely to occur. Return assumptions should reflect the uncertainty and risk of investing rather than being selected simply to produce a desired future balance.
Actual investment returns can vary significantly from year to year. Stocks, bonds, funds, and other investments have different risk characteristics, and none offers a guaranteed long-term return simply because a calculator uses a particular percentage.
Your investment horizon
Time can have a large effect on an investment projection because a longer horizon allows more contributions to be made and gives existing investments more opportunity to participate in future gains or losses.
Return assumptions also become increasingly important over long periods. Even a modest difference between two assumed annual returns can produce a much larger difference in projected ending values when carried across many years.
Increasing contributions over time
A fixed monthly contribution is not the only way to build a long-term investment plan. If you expect your ability to invest to increase, the annual contribution-increase input can illustrate what may happen when you gradually raise the amount you contribute.
Before relying on an aggressive increase assumption, consider whether the resulting future contribution level is realistic. A projection can look strong on paper while still requiring future deposits that may be difficult to maintain alongside housing, debt, family expenses, emergencies, and other financial priorities.
Why actual investment returns will not follow a smooth projection
An investment-growth projection is intentionally simpler than real market experience. Actual investments can rise sharply, decline, recover, or remain flat for extended periods, while a planning assumption represents future performance with a single annual rate.
This means the calculator should not be read as a forecast of what your balance will be in a particular year. Its stronger use is as a scenario-planning tool: change one or more assumptions and see how much the potential outcome depends on your contributions, time horizon, and assumed return.
Market volatility also means two investors can experience very different paths even when long-term average returns appear similar. The timing of gains, losses, deposits, and withdrawals can matter in real investment accounts.
Comparing two investment growth scenarios
Comparison mode uses the same starting investment while allowing Scenario A and Scenario B to use different monthly contributions, annual return assumptions, investment horizons, and annual contribution increases.
This makes it possible to test questions such as whether saving more could have a greater effect than assuming a higher return, how extending the investment horizon changes the projection, or how gradually increasing contributions may affect a long-term goal.
Pay particular attention to the breakdown of the ending-value difference. A scenario with a larger ending value may get there because you contributed substantially more money, because the return assumption produced more modeled growth, or because of a combination of both.
If you want to understand the effect of one particular decision, keep the other assumptions as similar as possible. For example, using the same horizon and return assumption while changing only the monthly contribution provides a clearer view of the contribution tradeoff than changing several assumptions at once.
When the horizons differ, remember that the comparison is no longer measuring only the effect of saving or investment performance. One scenario also has more time for contributions and potential growth, so the ending-value difference should be interpreted in that context.
Important assumptions and limitations
This calculator provides a hypothetical investment-planning illustration. It does not forecast market performance, recommend a particular investment, or guarantee that any assumed annual return will be achieved.
Real investment returns are variable and can be negative. Actual results can differ materially from a projection because of market conditions, asset allocation, security selection, volatility, and the timing of investment gains and losses.
Fees, taxes, trading costs, account expenses, and other charges can also reduce the value ultimately available to an investor. Their effect will depend on the investments and accounts you actually use and may not be fully represented by the return assumption entered in the calculator.
The calculator assumes that the contribution plan you enter can be maintained. Real contributions may be interrupted, increased, reduced, or withdrawn as financial circumstances change.
This tool is intended for investment-growth planning rather than bank-deposit calculations. If you want to model a stated bank interest rate with a specific compounding frequency, use the separate MarketReview Compound Interest Calculator.
Use the results to explore scenarios and tradeoffs, not as a substitute for evaluating investment risk, diversification, taxes, fees, liquidity needs, or your broader financial plan.
Related calculators
Building a stronger long-term investing plan
Investment projections are most useful when they help you test realistic saving habits, time horizons, and return assumptions rather than focus on a single future number. MarketReview's investing section covers more of the concepts that can help you evaluate long-term investment choices.