Mutual Fund Calculator
Project the future value of a mutual fund position with an initial investment, monthly contributions, expected annual return, and expense ratio drag over a chosen horizon.
Last updated: September 2026
Compare with similar
About this calculator
A mutual fund pools money from many investors to hold a diversified portfolio of stocks, bonds, or both. The value of the fund per share is the NAV (net asset value), reset each business day. Investors buy and sell at that day's NAV, which is why funds are said to trade 'once a day' — unlike ETFs which trade continuously.
Two forces drive the future value of a mutual fund position: contributions (initial + ongoing) growing at the fund's return, and expense ratio dragging that return down. This calculator uses the standard compound-interest math: future value = initial × (1+r/12)^n + monthly × ((1+r/12)^n − 1) / (r/12), where r is the annual return net of the expense ratio and n is months.
The expense ratio matters. A 1% higher expense ratio over 30 years reduces the ending balance by roughly 25%. Actively-managed mutual funds average 0.6–1.2% in expenses; index funds average 0.03–0.20%. The S&P 500 has returned roughly 10% nominally (7% real, after inflation) since 1926; use those as reference points for the 'expected annual return' input. A pure-bond portfolio typically returns 4–5% nominally; a 60/40 stock/bond mix, around 7–8%.
How to use
Example — a 20-year retirement account. Initial $10 000, $500/month contributions, 8% expected return, 1% expense ratio. Net return = 8 − 1 = 7% annually; monthly rate = 0.005833. n = 240 months. (1.005833)^240 ≈ 4.037. Future value of initial = 10 000 × 4.037 = $40 370. Future value of monthly contributions = 500 × (4.037 − 1) / 0.005833 = 500 × 520.5 = $260 250. Total ≈ $300 620. Now switch to a low-cost index fund at 0.05% expense ratio. Net return = 7.95%. Rerun: total ≈ $325 000. The lower expense ratio adds ~$25 000 — the price of the 1% drag over two decades. Compare paths against /en/calculators/investing/compound-interest/ for the pure-math version without expenses.
Frequently asked questions
Why does the expense ratio matter so much?
Because it compounds. A 1% higher annual fee reduces the ending balance by roughly (1 − 0.99^30) ≈ 26% over 30 years. On a $500 000 portfolio, that is $130 000 less at retirement — enough to buy a house or fund several years of retirement spending. Index funds at 0.03–0.20% expense ratios almost always beat actively managed funds at 0.60–1.20% expenses over long horizons; multiple decades of academic research (Fama-French, Bogle) support this conclusion.
What return should I assume?
For a 100% stock portfolio, 7% real (10% nominal minus 3% inflation) is the widely-used long-term US average. For a 60/40 balanced portfolio, 5–6% real (7–8% nominal). For bonds only, 1–2% real. Use conservative numbers for planning; if reality overshoots, you retire early. If you use aggressive numbers and the market underdelivers, you fall short of your goal.
How is a mutual fund different from an ETF?
Mutual funds price once daily at 4 PM ET; ETFs trade continuously like stocks. Mutual funds usually have higher expense ratios and sometimes 12b-1 fees (marketing costs); ETFs are almost always cheaper. Mutual funds allow fractional shares and automatic contributions easily; ETFs sometimes require whole shares. For long-term buy-and-hold in a tax-advantaged account, both work; ETFs typically win on cost and tax efficiency in a taxable account.
Does this account for taxes?
No. In a tax-advantaged account (401(k), IRA), no taxes apply until withdrawal. In a taxable account, dividends and capital gains distributions are taxable each year, dragging the net return down by 0.5–1.5% depending on the fund. For a taxable-account projection, reduce the expected annual return by 1% or use an ETF (which typically distributes fewer capital gains). See /en/calculators/investing/capital-gains-tax/ for detail.