Investment Calculator

This calculator takes a starting amount, a recurring contribution, a time horizon, an assumed annual return, and a compounding choice, then repeats the growth arithmetic over time. You can also enter an annual increase in the contribution and an inflation assumption. The output answers a narrow question: what does this set of assumptions produce?

It cannot answer what a market, fund, account, or portfolio will actually do. A constant return input is a modeling convenience. Real investment values can rise or fall; costs, taxes, missed contributions, withdrawals, and account rules can change an outcome. Use the page to compare transparent scenarios, not to turn a chosen percentage into a promise.

In each modeled period, the starting balance earns the rate implied by the annual return and selected compounding frequency, and the page adds the contribution according to the selected timing. If you choose a contribution increase, the next year’s monthly contribution is raised by that percentage. The table separates the total amount you contributed from the modeled growth so you can see which part comes from each input.

For a simple scenario, a $10,000 starting amount plus $500 each month is not the same calculation as $10,000 with no future deposits. A long horizon makes the timing of deposits relevant, and a different compounding setting changes the assumed periodic rate. The diagram identifies the inputs that should be reviewed before you compare outputs.

The lower, base, and higher return rows are deliberately not recommendations. They show how the same contribution plan changes when the assumed return changes. That makes the model more useful than hiding uncertainty behind a single default. If a goal only works in the highest displayed scenario, that is information about the assumption—not evidence that the outcome will occur.

The U.S. Securities and Exchange Commission’s Investor.gov compound-interest tool similarly asks for an estimated rate, contribution, time, variance range, and compounding frequency. Those inputs belong in the open because they drive the result.

A nominal projection shows the model’s dollar amount at the end of the selected period. When you turn on the inflation adjustment, the page divides that future nominal amount by the entered inflation factor to express it in today’s purchasing-power terms. Both outputs can be useful, but neither is a prediction of prices or a guarantee of what a future withdrawal can buy.

Try a controlled comparison: keep the starting amount, contribution, time, and return unchanged; change only the inflation input; then inspect the nominal and purchasing-power columns. The Inflation Calculator is a separate historical-data tool and should not be used to turn one past index series into a future certainty.

Use this page when you want to inspect growth with a chosen return assumption and regular contributions. Use the Savings Goal Calculator when the main question is a cash goal, deadline, deposit amount, and account rate. Use the Retirement Calculator when the inputs include retirement spending, age, other income, withdrawal rate, and a separate retirement-period assumption.

Each tool is a different model. Copying a result from one to another without matching the assumptions can make a plan look more precise than it is. Record the date you ran a scenario and the actual inputs used, especially if you later compare it with a different contribution or time horizon.

When comparing two projections, write down the date, starting balance, monthly contribution, contribution increase, years, return assumption, compounding choice, and inflation setting for each one. A final balance without that input record cannot be reproduced or meaningfully compared later. This is especially important when a contribution is expected to change or when a target is evaluated under several return assumptions.

Do not use a projection to hide cash-flow risk. A contribution that only works if income arrives every month is a different scenario from a flexible contribution that can pause. The calculator can illustrate either input pattern only through reruns; it cannot estimate job stability, emergency costs, taxes, account limits, or the effect of withdrawals on a real portfolio.