Investment Calculator
Project how an initial amount plus monthly contributions could grow at a chosen return, with an inflation-adjusted value in today’s dollars.
How it works
Each month: balance = balance × (1 + r) + contribution · Real value = balance ÷ (1 + inflation)^years
The initial amount and every monthly contribution compound at the monthly rate derived from your annual return and compounding choice. Because growth builds on prior growth, the final years add the most. The inflation line divides the ending balance by cumulative inflation so you can read the result in today’s buying power, which is what the money will actually feel like when you spend it.
Worked example
$10,000 plus $300 a month at a 7% return compounded monthly for 20 years grows to about $196,665 — $82,000 of it contributions and roughly $114,665 growth. At 2.5% inflation, that balance is worth about $120,019 in today’s dollars.
Frequently asked questions
What return should I assume?
A diversified stock-heavy portfolio has historically returned about 7% a year after inflation over long periods, with large swings year to year. Model a range rather than betting on one number.
Why show an inflation-adjusted value?
A six-figure balance decades from now buys less than it sounds. Dividing by cumulative inflation restates it in today’s dollars, so you can judge whether the goal actually covers future costs.
Does compounding frequency change much?
Only modestly. The return you earn and the number of years you stay invested drive the outcome far more than whether interest compounds monthly or daily.
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Educational estimate, not investment or tax advice. Returns are never guaranteed and past performance does not predict the future. Confirm with a licensed advisor.