Projecting an investment portfolio means accounting for more than just a return rate. Fees compound against you the same way returns compound for you, inflation quietly erodes purchasing power over long horizons, and a rising contribution can meaningfully change where you land. This calculator models all three, so the projection reflects what you'd actually experience rather than an idealized number.
How to Use This Investment Calculator
Enter your initial investment and planned monthly contribution, an expected annual return, and how many years you plan to stay invested. In the advanced section, add an annual fee or expense ratio if your investment carries one, an annual percentage increase to your contribution (to model rising income), and an expected inflation rate to see your result in today's purchasing power alongside the nominal figure.
How Investment Growth Is Calculated
Each month, this calculator applies your expected return to the current balance, deducts any fee from that same balance, and then adds your contribution. Fees are charged on assets under management — the balance before that month's contribution — which is how expense ratios actually work in practice. Contributions can also increase annually if you specify a rate, modeling a saver whose contribution grows alongside their income.
The Effect of Fees and Inflation
A 1% annual fee doesn't just cost 1% of your balance in a given year — it costs 1% of a balance that would otherwise have kept compounding, so the gap between a low-fee and high-fee portfolio widens every year you stay invested. Inflation works differently: it doesn't reduce your account balance, but it reduces what that balance can buy. This calculator reports both your nominal final balance and that same balance restated in today's dollars, discounted by your assumed inflation rate.
Example Calculation
$10,000 invested with a $500 monthly contribution, a 7% expected annual return, and a 0.5% fee, over 25 years, grows to roughly $436,000 nominal. Assuming 3% average inflation over that period, that balance is worth about $208,000 in today's purchasing power — a useful reminder that a large future number and its real value can differ substantially.
What Affects Your Investment Outcome
- Time in the market — the longest lever available; more years means more compounding, and compounding accelerates rather than staying flat.
- Contribution amount — for most people investing over decades, contributions matter as much as or more than the return rate itself.
- Fees — a seemingly small percentage becomes a large dollar cost over a long enough horizon.
- Inflation — doesn't change your account balance, but changes what that balance is actually worth when you go to spend it.