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Free · Expense ratios · Boglehead-friendly

Index fund calculator

Project growth of a total-market or S&P 500 index fund over decades. Set your expected return after fees and see exactly how compounding builds wealth on autopilot.

Direct answer

How much does a total-market index fund grow over 30 years?

A $10,000 lump sum plus $500 monthly contributions at a 9% assumed annual return grows to approximately $1,020,000 over 30 years. Total contributed: $190,000; total growth: $830,000. Your result changes with the return, contribution timing and the fund's current expense ratio.

Compare the current prospectus for each fund before entering its expense ratio. Fees, holdings, tax treatment and tracking difference can change; this projection is an illustration, not a fund recommendation.

Source: Illustrative compound calculation; verify fund terms with the provider

Index fund quick facts

  • Expense ratio input: Use the latest provider prospectus
    SEC Investor.gov
  • Net return assumption: Gross return minus fees and other costs
    Illustrative model
  • Fund comparison: Review fees, tracking difference, holdings and taxes
    Investor.gov
  • Fee impact: Small annual costs compound over long periods
    Illustrative compound math
Index fund expense ratios that matter · SEC Investor.gov investor education
Expense ratios reduce the return you keep
Enter the fund's current expense ratio from its prospectus. The calculator subtracts that cost from the return assumption so you can compare scenarios on the same basis.
The page separates the model's assumptions from live fund terms, which can change and should be checked with the provider.

Expense ratios — the silent drag

Every index fund charges a small annual fee, expressed as the expense ratio. It's tiny but compounds against you for decades. To project net returns, subtract the expense ratio from your assumed gross return.

Fund costs change. Check the latest prospectus for the exact expense ratio, trading costs and any account fees before you enter a value.

The dollar impact depends on your balance, contributions, return assumption and time horizon. Run both fee scenarios in the calculator, then compare the complete cost and tracking record rather than choosing on the expense ratio alone.

What return assumption should I use?

These are illustrative scenarios, not forecasts. Test a range and include fees, taxes and inflation in your plan.

  • Broad US equities: 7–10% nominal scenario
  • Inflation-adjusted equities: 4–7% real scenario
  • Balanced stock/bond mix: 4–7% nominal scenario

$500/month in a total-market index fund

Years7% real9% nominal10% nominal
10$86k$96k$102k
20$259k$330k$378k
30$606k$905k$1.13M
40$1.30M$2.25M$3.16M

Index Fund Calculator FAQ

Which index fund should I pick?

Common building blocks include total-US, S&P 500 and international index funds, but fees, holdings, taxes and availability vary by provider. Check each fund's current prospectus and choose an allocation that fits your goals and risk tolerance.

Is the S&P 500 going to keep returning 10%?

Nobody knows. Historical averages describe a selected time period and do not predict the next one. Test several nominal and real assumptions, include fees, taxes and inflation, and review the plan as your time horizon changes.

How does this calculator handle dividends?

It assumes total return — dividends are reinvested back into the fund. Real-world index funds in an IRA or 401(k) auto-reinvest by default. In taxable accounts, dividend distributions are taxed at qualified rates (0–20%) the year they're paid.

Index funds vs ETFs — same thing?

Functionally yes, structurally a bit different. Mutual fund index versions (VTSAX) settle once daily at NAV. ETF versions (VTI) trade like stocks throughout the day. ETFs are slightly more tax-efficient in taxable accounts due to the in-kind redemption mechanism. Same underlying holdings.

Should I time the market with index funds?

No strategy can reliably predict short-term market moves. Choose a contribution schedule you can maintain, account for your time horizon and risk tolerance, and avoid treating a smooth projection as a promise.

What about index fund crashes?

Total-market and S&P 500 indexes have drawn down 50%+ multiple times (2000–2002, 2008–2009, 2020) and recovered every time. The key is staying invested. The calculator's smooth curve hides this — assume your real path has stomach-turning dips and a long-term upward slope.

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Index funds + savings rate = FIRE.

Methodology and editorial standards

Each calculator uses its own inputs and method. Review the labels, units and assumption notes shown with the result. Costs, taxes, fees, benefits and other factors are not modeled unless the page or calculator explicitly says they are. A fixed-rate projection is a scenario, not a forecast or personalized recommendation.

The editorial standards explain how Snowballr reviews calculators and sources. The sources index links to references used across the site. To report an error or suggest a correction, use the contact page.