Quick answer
An investment calculator projects portfolio growth from an initial investment plus regular contributions, net of fees. $25,000 invested with $400 a month at an 8% average annual return, less 0.5% fees, grows to about $333,013 in 20 years — $121,000 contributed and roughly $212,013 of growth.
How the Investment Calculator works, step by step
Enter the initial amount, monthly contribution, expected annual return, annual fees, inflation and horizon — or pick a scenario: Conservative at 5%, Base at 8% or Aggressive at 11%. The calculator compounds monthly at the return net of fees, so each contribution starts growing the month after it is invested and the existing balance compounds throughout.
Fees are a first-class input, not a footnote. The tool shows the ending balance with fees and without them, and the difference is the fee cost. On the worked example, 0.5% a year costs $25,766 over 20 years: $358,778 without fees against $333,013 with them. A fund charging 1% a year against one charging 0.1% turns an 8% market return into 7% versus 7.9% — the gap compounds exactly like the return does.
Read the three scenarios as the honest range, not a forecast. Net of the default 0.5% fees, the same $25,000 and $400 a month reaches about $216,636 at the Conservative 5% return, $333,013 at Base 8% and $526,500 at Aggressive 11%. The spread between the low and high cases is over $300,000 — that uncertainty is the real content of a 20-year projection.
Compare the contribution total with the growth total in the results. Early in the horizon, contributions dominate — your saving rate is the engine. Later, growth dominates — the portfolio's return is the engine. In the worked example, growth supplies about two-thirds of the end value. That crossover is the point at which investment decisions start to matter more than budget decisions.
The tool also shows the result in today's money: at 3% inflation, the $333,013 example is worth about $184,381 in real terms. What it does not model is volatility or tax. Real returns arrive unevenly, including falls of 30% or more, and the smooth line will never match a real account statement. In a taxable account, dividends and realised gains are taxed along the way; in an IRA or 401(k), the balance shown is pre-tax and withdrawals may be taxed.
The formula
Future value = Initial × (1 + m)^(12t) + Monthly × [((1 + m)^(12t) − 1) / m], where m = (annual return − fees) ÷ 100 ÷ 12 and t the years. Real value = nominal value ÷ (1 + inflation)^t.
Worked example — try it on the calculator above
Worked example: $25,000 plus $400 a month at 8% for 20 years
At 8% less 0.5% fees, the net return is 7.5%. The initial $25,000 compounds to about $111,500 and the 240 contributions of $400 — $96,000 paid in — grow to about $221,500. Combined future value: roughly $333,013, with growth supplying about two-thirds of the end value. Without fees the same plan reaches $358,778. Cut the gross return to 6% and it ends near $267,571 before fees, which is the sensitivity to keep in mind before treating any projection as a promise.
Frequently Asked Questions
Should I use pre-tax or after-tax returns?
For money in an IRA or 401(k), project the account balance with pre-tax returns and remember withdrawals may be taxed (traditional) or not (Roth). In a taxable account, dividends, interest and realised gains are taxed along the way, so an 8% gross return might compound at closer to 7% after tax depending on the investments and your bracket.
How do investment fees affect the projection?
Subtract them from the return. A fund charging 1% a year against one charging 0.1% turns an 8% market return into 7% versus 7.9%. On the worked example, compounding at 7% instead of 7.9% cuts the 20-year result from about $353,000 to about $309,000 — roughly $44,000 paid for the fee difference.
What return should I enter for a 60/40 portfolio?
Historical nominal returns for a 60% stock / 40% bond mix have been around 8% over very long periods, but forward-looking planner assumptions are often 5% to 7% because bond yields and valuations change the outlook. Model the lower figure for decisions you cannot afford to get wrong, like a retirement date.
Does the calculator include inflation?
Results are nominal, but the tool shows the inflation-adjusted value alongside: at 3% inflation, divide the result by about 1.81 for a 20-year horizon to see today's purchasing power — the $333,013 example is roughly $184,381 in today's money. Decisions about whether a plan is 'enough' should always be made in real terms.
Estimates, not advice. This calculator provides educational estimates based on the inputs you enter and the assumptions shown on this page. It is not financial, tax or investment advice, and it cannot see your full situation. Verify important figures against official sources, and consider a qualified professional for decisions about your own money. See our Disclaimer and Methodology.