Portfolio Growth Calculator

The formula

With monthly contributions added at the end of each month and monthly compounding at a net rate i = (gross − fee) ÷ 12, the balance after N months is:

We run the same formula twice — once at your gross return and once at your net return (gross minus annual fee). The gap between the two final balances is your total fee cost.

How the numbers split out

• You contributed = starting portfolio + all monthly contributions (your own money).
• Investment growth = the growth you'd earn with no fees, before fees are taken out.
• Fees paid = the difference between the no-fee and the net-of-fee final balance — what fees cost you over the whole period.
• Final value = contributions + growth − fees. The three always add up exactly.

Assumptions

• The annual fee is subtracted from the gross return before compounding (net-of-fee rate) — a standard simplification used by most investment fee calculators.
• Contributions are added at the end of each month (ordinary annuity).
• Returns are nominal, pre-tax; fees and inflation are constant over the whole period.
• No market volatility is modeled — the return rate is assumed constant.
• Results are hypothetical and for education only — not financial advice.

Example 1: $50,000 + $1,000/month for 30 years

Return: 7% · Annual fee: 0.2% · Inflation: 3%

After 30 years of investing $1,000/month (plus $50,000 to start), your portfolio grows to a nominal $1,555,226. But here's the critical distinction: after adjusting for 3% annual inflation, that money only has the purchasing power of $640,732 in today's dollars. You contributed $410,000 of your own money, meaning nominal investment growth was $1,145,226 (74% of the final balance). This is why "millionaire" status means less than it used to — $1M in 30 years will only buy what ~$412,000 buys today at 3% inflation. Always plan in real, inflation-adjusted terms, not nominal numbers.

Example 2: The hidden cost of a 1% fee

Same $50k + $1k/month, 7% return, 30 years · 0% fee vs 1% fee

A 1% annual fee sounds small — it's just 1% of your balance each year. But over 30 years, that 1% compounds into $320,152 of lost wealth — nearly 20% of what you would have had without the fee. Put another way, the fee provider collects more from you over 30 years ($320k) than your entire initial $50,000 investment. This is why John Bogle (founder of Vanguard) spent his career preaching about fees: "In investing, you get what you don't pay for." A 0.2% ETF fee vs. a 1% mutual fund fee costs you $256,000 over 30 years in this scenario. Fees are the one thing in investing you can control — returns you can't.

Example 3: Inflation's silent erosion

Same nominal $1,555,226 after 30 years · different inflation rates

The same nominal $1,555,226 buys very different amounts depending on inflation. At 2% (the Fed's target), it's worth $861,897 in today's dollars. At 3% (the long-term average), $640,732. At 5% (a high-inflation scenario like the 1970s), just $359,844 — less than a quarter of the nominal number. This is why retirees on fixed incomes are devastated by high inflation: their nominal dollars stay the same, but each dollar buys less every year. Your investment plan must include an inflation assumption, and you should hold assets that historically outpace inflation (stocks, real estate, TIPS). A 7% effective nominal annual return and 3% inflation give about 3.88% real annual return — that's the number that actually matters for your lifestyle. Try our Inflation calculator to explore this further.