Investment Calculator

This calculator looks forward: you set a starting amount and a monthly contribution, and it projects the balance after a number of years. Behind the result:

• the annual return is split into twelve monthly rates (rate ÷ 12) and compounded monthly;
• each contribution goes in at the start of the month, so it earns that month's growth;
• the contribution and the return stay the same every year;
• there are no taxes, fees, withdrawals or inflation adjustments.

With the defaults, $10,000 plus $500 a month at 8% for 20 years projects to $345,741.64. You put in $130,000, and the estimated growth is $215,741.64.

Change one default at a time to see where your effort pays off:

One point less return costs $43,371.55 over 20 years. That is also roughly what a 1% yearly fee does to an 8% return, which is why costs belong in the rate you enter. Ten extra years more than doubles the result, because growth in the later years is earned on a much bigger balance.

The future value is in future dollars. To see what it would buy today, divide by (1 + inflation)^years. Assuming 3% inflation, $345,741.64 in 20 years is worth about $191,428.76 in today's money.

Another approach is to enter a return with your inflation assumption taken off, 5% instead of 8%, and read the result as today's dollars. That gives $233,499.56, higher than the figure above, because it quietly treats your $500 as rising with inflation every year. Use the first method if your contribution will stay at $500, and the second if you plan to raise it in line with prices.

• Timing. If you contribute at the end of each month instead, the 20-year default comes to $343,778.24, $1,963.40 less.
• Zero return. At 0% the result is simply your contributions: $130,000 at the defaults.
• Rising contributions. The tool keeps the monthly amount flat. If you plan to raise it as your pay rises, the result here is an underestimate.
• Account limits. If the money goes into a tax-advantaged account, the yearly limit caps how much you can contribute. For tax year 2026 the IRS limits are $24,500 of elective deferrals to a 401(k) and $7,500 to IRAs (traditional and Roth combined), with higher catch-up amounts from age 50. The default $500 a month is $6,000 a year.