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Investment Calculator — See How Your Money Grows Over Time

Use this free investment calculator to project future value, solve for required savings or return, and see how starting balance, contributions, compounding, and time work together. Switch tabs to target ending balance, contribution amount, rate, starting principal, or investment length — then review charts and annual or monthly schedules.

Each tab solves for a different variable. For tax and inflation on interest, see the Interest Calculator.

Enter the known fields for the active tab, then click Calculate.

After (investment length)
Contribute at the
of each

Results

Pick a tab, enter values, and click Calculate to see projections.

How to use

  1. Choose which variable to solve for: end amount, contribution, return rate, starting amount, or length.
  2. Enter the remaining inputs (starting balance, term, rate, compounding, contribution timing and frequency, and goal balance when needed).
  3. Click Calculate to see the solved value (if applicable), ending balance, totals, donut, line chart, stacked year view, and schedules.
  4. Use conservative return assumptions for real planning; pair with the Interest Calculator for inflation and tax scenarios.

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How this investment calculator works

The tabs let you solve for one unknown at a time: ending balance, starting lump sum, periodic contribution, annual return, or time horizon. The engine steps month by month, applying a growth factor consistent with your compounding choice and adding contributions at the beginning or end of each month or year.

For “annually” compounding, each month uses the twelfth root of (1 + annual rate) so that twelve monthly steps match one year of the stated annual return — the same convention used by many public investment calculators. Other frequencies map to an equivalent per-month factor in a similar way; monthly uses the nominal rate ÷ 12 per month.

The main variables

  • Return rate — assumed average annual percentage; actual markets vary year to year.
  • Starting amount — today’s lump sum invested immediately.
  • Additional contribution — repeated deposit each month or year.
  • Investment length — how long the plan runs before you read off the balance.
  • End amount — future value; can be an output or a goal for other tabs.

Limits and caveats

Real portfolios have fees, taxes, irregular returns, and cash flows. This tool is for education and rough planning — not a forecast. For tax, inflation, and more control over timing, use the Interest Calculator or dedicated retirement tools alongside this one.

Frequently asked questions

Growth, return assumptions, contributions, and basic stock vs bond concepts.

How do I calculate investment growth?

Long-term growth combines compound returns on your starting balance and on each additional contribution. With a fixed assumed return and timing of deposits, a month-by-month simulation (as in this calculator) matches how most planning tools project balances. For irregular returns, treat the rate as an average and use conservative assumptions.

What is a realistic return rate to use?

It depends on the asset mix. Many planners use roughly 6–7% nominal for long-term diversified stock-heavy portfolios, or lower for balanced or bond-heavy mixes. Past averages are not guarantees — using a conservative rate for important goals reduces the risk of falling short.

How much should I invest per month?

It depends on your goal, timeline, and expected return. This calculator’s “Additional Contribution” tab works backward from a target ending balance. Rules of thumb (such as saving a set percentage of income) are starting points; your number should fit your budget and emergency fund first.

What is the difference between stocks and bonds?

Stocks represent ownership in companies and historically have higher long-term volatility and expected returns than bonds. Bonds are loans to governments or corporations with more predictable income and typically lower long-term returns than stocks. Most long-term portfolios mix both based on time horizon and risk tolerance.

How does compound interest differ from simple interest?

Simple interest applies only to the original principal. Compound growth applies to prior gains as well, so balances can accelerate over long periods. This calculator uses compounding aligned with the frequency you select (e.g., effective monthly steps for “annual” compounding).

What is an ETF and how is it different from a mutual fund?

Both pool money to buy a basket of assets. ETFs usually trade on exchanges at market prices throughout the day; traditional mutual funds often price once daily. Cost structures differ by fund. This calculator does not model fund fees — you can approximate them with a lower net return rate.

How do I know if an investment is too risky for me?

Consider when you need the money and whether you could stay invested through a large drawdown. Shorter horizons usually call for more stability (cash and high-quality bonds). Longer horizons can often tolerate more equity volatility. This tool does not replace a personalized risk assessment.

Who uses this calculator

People projecting retirement or college balances, comparing how different return assumptions change outcomes, working backward from a goal to a monthly savings amount, and anyone who wants a year-by-year or month-by-month view of compound growth with steady contributions.