Investment Calculator

At a 7% average annual return compounded monthly, $10,000 grows to about $40,387 in 20 years. Add $500 of monthly contributions and the same period ends near $300,851, of which $130,000 is money you deposited. The investment calculator above lets you substitute your own numbers for any of these inputs.

Use a long-term average that matches your asset mix. Broad stock-market indexes have historically returned roughly 7% per year after inflation over multi-decade periods; balanced stock/bond portfolios have averaged less. Model a conservative case (4–5%), a base case (7%) and an optimistic case (9–10%) rather than trusting one number, and remember past performance does not guarantee future results.

Each contribution starts compounding the month it is deposited, so early contributions are worth far more than late ones — a dollar added in month 1 compounds for 239 months in a 20-year plan, while the final dollar compounds for none. This is why the ordinary-annuity formula, not simple addition, is used for the contribution stream.

The math is the same family — future value with compounding — but savings accounts typically pay a fixed advertised APY with no contributions, while investment projections assume a variable market return you must estimate. For a savings-account-style calculation with custom compounding frequencies, use the compound interest calculator; for market-return projections with monthly deposits, this investment calculator is the better fit.

No — the projection is nominal and pre-tax. To approximate inflation, lower the return rate by expected inflation (e.g. model 7% nominal as 4–5% real). To approximate tax drag in a taxable account, reduce the rate by your estimated annual tax cost. Tax-advantaged accounts such as a Roth IRA can be modeled at face value, which is why pairing this tool with a Roth IRA projection is useful.

It is an exact month-by-month simulation of the stated assumptions: monthly compounding at a constant rate with end-of-month contributions. Its final balance matches the headline figure to the cent. What the table cannot show is real-world variance — actual annual returns swing far above and below the average, so treat the path as illustrative and the endpoint as an estimate.

This tool answers 'what will my investments be worth?' given deposits, rate and time. The retirement calculator starts from a spending goal and works backward to the savings required, and the SWP calculator handles the withdrawal phase after you stop contributing. Use them in sequence: project the balance here, then test whether it funds the retirement income you need.