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Investment Calculator (Growth, Fees & Inflation)

Free investment calculator for 2026. Project growth from an initial sum plus monthly contributions, then see what fees and inflation cost you. No sign-up.

Last reviewed: January 2026 · Tax data verified against IRS Publication 15-T & state revenue departments

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How This Calculator Works

This calculator answers a portfolio question, not a savings-account question: given an initial sum and a monthly habit, what do you actually end up with - after the expense ratio you pay, and restated in money you can spend? Most growth calculators stop at the nominal number, which flatters the plan twice: once by ignoring the 0.05%-to-1% fee silently skimmed every year, and once by letting a 2046 dollar masquerade as a 2026 dollar. Here both drags are on the label.

The engine is the standard monthly-compounded annuity: the initial investment grows at the net return (expected return minus fee), each monthly contribution lands at month-end and compounds from there, and the future value is the sum. On the defaults - $10,000 initial, $500 a month, 7% expected return, 0.05% fee, 20 years - the plan reaches $298,875.65 nominal on $130,000 of deposits: $168,875.65 of growth did the heavy lifting.

Then comes the translation most people skip. At 3% inflation, prices multiply by about 1.806 over 20 years, so dividing the nominal pile by that factor gives its real value: $165,480.20 in today's dollars. Both numbers are true - they describe the same cash measured against different price levels. Planning on the nominal figure alone is how a target that looked like $300,000 arrives feeling like $165,000 did.

The fee experiment below is the differentiator worth staring at. The identical plan at a typical 1% active-fund fee ends at $264,122.49 instead of $298,875.65 - a $34,753.16 lifetime difference for the same deposits, same market, same patience. Fees compound against you exactly the way returns compound for you: every dollar skimmed in year one never gets to grow for the remaining nineteen.

What this projection deliberately leaves out is taxes on the growth, because the account wrapper decides that part. In a taxable brokerage account, long-term gains run 0%, 15%, or 20% federally (plus a 3.8% NIIT at higher incomes) - our capital gains calculator prices that drag. Inside a 401(k) or Roth, the wrapper changes everything: a match is free money (see the 401(k) calculator) and Roth compounding is tax-free (see the Roth IRA calculator).

How It's Calculated

Formula

FV = P x (1+i)^m + PMT x [((1+i)^m - 1) / i] where i = (return% - fee%) / 12, m = 12 x years | Real FV = FV / (1 + inflation%)^years

Step-by-Step

  1. 1Compute the net return: expected return minus expense ratio (7% - 0.05% = 6.95%)
  2. 2Convert to a monthly rate: i = 6.95% / 12 = 0.5792% per month
  3. 3Grow the initial investment by (1+i)^m where m = months
  4. 4Add the monthly contribution stream as an ordinary annuity: PMT x [((1+i)^m - 1) / i]
  5. 5Divide the nominal result by (1 + inflation)^years to restate it in today dollars
  6. 6Re-run with a different fee to quantify fee drag - the shortfall is the lifetime fee cost

Example

$10,000 initial + $500/month at 7% with a 0.05% fee for 20 years: i = 0.0695/12. FV = 10000 x (1+i)^240 + 500 x [((1+i)^240 - 1)/i] = $298,875.65 nominal. Inflation-adjusted at 3%: 298,875.65 / 1.03^20 = 298,875.65 / 1.806111 = $165,480.20 in today dollars. Total invested: $130,000.00; growth: $168,875.65. At a 1% fee the same plan ends at $264,122.49 - the fee difference alone is $34,753.16.

For detailed data sources and full methodology, see our Methodology & Data Sources page.

Key Rates & Data for 2026

S&P 500 long-run average

~10% nominal / ~7% real (historical)

Typical planning return (diversified)

5% to 7% per year (typical)

Typical index fund expense ratio

0.03% to 0.20% (typical)

Typical active fund expense ratio

0.5% to 1%+ (typical)

Long-run U.S. inflation

~3% per year (historical average)

2026 long-term capital gains

0% / 15% / 20% + 3.8% NIIT

Frequently Asked Questions

What return should I assume for my investments?

Start from what the money is invested in, then subtract costs. U.S. large-cap stocks have averaged roughly 10% a year nominal over the long run - about 7% after inflation (historical, not a promise) - while a diversified 60/40-style portfolio has historically landed nearer 7-8%, and bonds less. For planning, most practitioners dial down to 5-7% nominal so one bad decade cannot wreck the plan. Two adjustments matter more than decimal-point precision: subtract your expense ratio (this calculator does it for you), and remember that your final working years carry sequence-of-returns risk - the average is not the experience. If your plan only works at 10%, the plan is fragile.

Do investment fees really matter that much?

More than almost anything else you control. Run the same $10,000 initial plus $500 a month at 7% for 20 years: at a 0.05% index-fund fee the plan reaches $298,875.65; at a typical 1% active-fund fee it reaches $264,122.49. The fee difference is 0.95 percentage points a year; the lifetime difference is $34,753.16 - more than a quarter of everything you deposited. Fees compound against you: every dollar the fund skims in year one never compounds for the remaining nineteen. Low-cost index funds typically charge 0.03-0.20%; many active funds charge 0.5-1%+ without reliably beating their benchmark after costs. If you change one thing after this calculator, check your expense ratio.

What does inflation-adjusted or 'today's dollars' mean?

It restates future money in today's purchasing power. At 3% average inflation, prices multiply by about 1.806 over 20 years, so a dollar in 2046 buys roughly 55 cents of today's goods. Dividing the nominal balance by 1.806 gives the real balance: the default plan ends at $298,875.65 nominal but $165,480.20 in 2026 dollars - the same pile of cash measured against different price levels. Planning only on the nominal figure is how people discover at 65 that their 'million' buys what $554,000 buys today. A useful shortcut: subtract inflation from your return (7% - 3% = 4% real) and project with that; this calculator shows both views side by side instead.

How are my investment gains taxed?

In a regular taxable brokerage account, the growth shown here is not what you keep. Long-term capital gains on assets held over a year are taxed at 0%, 15%, or 20% depending on income, plus a 3.8% net investment income tax above $200,000 single / $250,000 joint. Qualified dividends get the same treatment; ordinary dividends and interest are taxed as regular income. Mutual funds can also distribute taxable gains annually even if you never sell. The wrappers change the math completely: a 401(k) compounds tax-deferred, a Roth compounds tax-free, and an HSA is deductible going in and tax-free out for medical costs. Price the taxable bite with our <a href="/capital-gains-calculator">capital gains calculator</a>, or model the wrapper with the 401(k) and Roth IRA calculators.

Is a lump sum better than monthly contributions?

Both work; they do different jobs. A lump sum gets the longest possible time in the market, and historically money invested earlier has tended to outperform waiting - but most people do not have a lump sum, and monthly contributions are how real portfolios get built: automatic, boring, and immune to market-timing temptation. A fair way to hold it: the lump sum wins on expected value, dollar-cost averaging wins on behavior and sleep. This calculator supports both at once - enter existing savings as the initial amount and the automatic transfer as the monthly figure. Deciding whether to invest a bonus all at once or over twelve months? Run both scenarios here and see how small the difference is at your horizon.

How is this different from the compound interest calculator?

The <a href="/compound-interest-calculator">compound interest calculator</a> answers 'how does a starting balance plus monthly savings snowball?' - pure growth, Rule of 72, milestones, zero subtractions. This one answers 'what does my portfolio actually deliver after the drags?' - it subtracts your expense ratio before projecting and restates the ending balance in today's dollars, so the number you see is spendable, not just large. They share the same underlying annuity math; the difference is what each one removes. Use the compound tool for motivation and savings goals, this one for fee comparison and inflation reality, and the <a href="/401k-retirement-calculator">401(k) calculator</a> when an employer match and contribution limits are in play.

What about investing inside a 401(k) or Roth IRA?

The account wrapper matters almost as much as the return. A 401(k) with a match is the single best first dollar most people can invest: the match is an instant 50-100% return no market offers, up to the 2026 elective deferral limit of $24,500. Roth contributions compound completely tax-free, and qualified withdrawals in retirement cost nothing on decades of gains - which changes which of this calculator's numbers you care about, because for a Roth the nominal figure is much closer to what you keep. This projection is pre-tax by design, so treat it as the account-level view: for match modeling use the <a href="/401k-retirement-calculator">401(k) calculator</a>, and for the contribute-now-vs-withdraw-later tradeoff see the <a href="/roth-ira-calculator">Roth IRA calculator</a>.

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<a href="https://thetaxcalc.com/investment-calculator" title="Investment Calculator 2026 — Growth Net of Fees & Inflation">Investment Calculator 2026 — Growth Net of Fees & Inflation</a>

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