Stock Investment Calculator

Before you enter your numbers

Use the amount actually invested and a recurring contribution in the same currency. Decide whether dividends are reinvested. If they are, use a total-return assumption; if not, account for withdrawn dividends separately rather than assuming all returns continue compounding.

• Starting investment
• Monthly investment
• Years
• Assumed annual return

Input reference

• Starting investment: The current balance committed to this goal. Use a recent statement and exclude money reserved for unrelated goals. This starting value is already invested, so do not also enter it as a recurring contribution.
• Monthly investment: New money added at the end of each month. Convert annual saving to a monthly amount by dividing by 12. This page does not schedule skipped months or one-time deposits automatically.
• Years: The duration of the calculation in years. Longer periods give growth or withdrawals more time to operate. This is a chosen modeling horizon, not a prediction of an investment term or your lifetime.
• Assumed annual return: An assumed nominal annual rate, divided by 12 in monthly projections. It is held constant. It is not a guaranteed yield, and the default should be replaced with an assumption suited to your scenario.

Formula and calculation method

The balance grows at annual return / 12 before each month-end contribution. Total contributed money is the starting balance plus deposits. Estimated growth is the difference between projected value and contributed money, with no separate deduction for taxes or trading fees.

Worked example

At zero return, 5,000 initially plus 100 monthly for ten years becomes 17,000. Every unit of the increase is new saving. Positive returns add growth, while a stock that permanently loses value can perform far worse than a smooth positive projection.

How to interpret the result

The result panel reports projected value, total invested and estimated gain.

A single company can face concentrated business risk that a constant-rate model cannot describe. Stock splits do not themselves create value, and a rising share count is not the same as a higher total return. Consider how much of your wider plan depends on one employer or company.

Use return assumptions as scenarios—not predictions

The calculator grows a starting stock investment and recurring monthly purchases at the annual return you enter. It is useful for comparing contribution schedules, but it does not forecast an individual stock’s future price.

Individual stocks can be far more volatile than diversified funds. Test a wide range of returns, including negative scenarios, rather than relying on one historical growth rate.

Account for concentrated exposure outside the portfolio

An employer stock holding can link investment risk with employment income. If the company struggles, both the portfolio and salary may be affected. This calculator evaluates only the invested balance and cannot assess that household concentration.

A regular purchase plan does not guarantee a profit or prevent a permanent loss. It changes when money is invested. Use the projection to understand contributions and compounding, while evaluating the business exposure and liquidity separately from the attractive shape of a growth curve.

Use this as a scenario for a stock position, not a price forecast

The calculator compounds the return rate you enter; it does not forecast a company’s share price. A single stock can have much wider outcomes than a diversified portfolio, including permanent loss, so the assumed return should not be interpreted as a likely result simply because it is mathematically smooth.

If dividends are central to the investment thesis, decide whether your return assumption already includes them. Do not add a dividend return on top of a total-return assumption that already includes reinvested dividends.

Use The Result In The Next Calculation

Use this projection to test a stock-investment scenario, then use the stock return calculator when you have actual purchase and sale values. A projected return assumption and a measured historical return answer different questions.