To calculate investment turnover, take the lesser of a fund’s total securities purchases or total securities sales during the fiscal year, divide by the monthly average value of the portfolio securities the fund held that year, and multiply by 100. The result is a percentage: 50% means roughly half the portfolio changed hands over twelve months. The SEC prescribes this formula in Form N-1A, the registration document every mutual fund and ETF files, so the number in a prospectus is calculated the same way across the industry.1Securities and Exchange Commission. FORM N-1A
The Formula, Step by Step
There are two pieces to build.
The numerator. Compare the total dollar amount of securities the fund purchased during the fiscal year against the total dollar amount it sold. Use whichever figure is smaller. Taking the lesser figure prevents inflated turnover in years when heavy investor inflows forced unusual buying or heavy redemptions forced unusual selling. The point is to isolate trading the manager chose to do.
The denominator. The denominator is the monthly average value of the portfolio securities the fund owned during the fiscal year. To get it, add the portfolio’s value at the beginning of the first month, the value at the end of that month, and the value at the end of each of the eleven months that follow. That gives you thirteen data points. Divide the sum by thirteen.1Securities and Exchange Commission. FORM N-1A
Then divide the numerator by the denominator and multiply by 100.
A worked example: a fund makes $50 million in purchases and $70 million in sales during the year, against $100 million in average portfolio securities. The lesser figure is $50 million. Divide by $100 million, multiply by 100, and the reported turnover rate is 50%.1Securities and Exchange Commission. FORM N-1A
A Common Miscalculation to Avoid
Plenty of online explanations describe the denominator as “average net assets.” That is wrong. Form N-1A specifically requires the monthly average value of portfolio securities owned by the fund. Net assets include cash, receivables, and other items that aren’t portfolio securities. Substituting net assets pulls the denominator up and understates the turnover rate, sometimes meaningfully for funds that carry large cash positions.1Securities and Exchange Commission. FORM N-1A
Trades That Don’t Count
Not every transaction feeds the calculation. The SEC strips certain categories out of both the numerator and denominator so the turnover figure reflects genuine investment decisions rather than routine cash management. The exclusions come from Form N-1A, Item 13, Instruction 4(d):1Securities and Exchange Commission. FORM N-1A
- Securities whose maturity or expiration was less than one year at the time the fund acquired them. This covers Treasury bills, commercial paper, repurchase agreements, and similar short-term instruments used to park cash.
- Options and futures contracts with expirations less than one year from acquisition. Puts and calls with expirations beyond one year are included, with premiums paid counted as purchases and premiums received counted as sales.
- Securities acquired when the fund takes on another fund’s assets in exchange for its own shares. The denominator is adjusted to reflect the exclusion.
One point trips people up: long-term government bonds stay in. Only short-term government obligations fall out. A ten-year Treasury note bought and sold within the fiscal year counts toward turnover.
Where to Find the Number Without Doing the Math
You rarely need to run the calculation yourself. Every fund prospectus reports the portfolio turnover rate for the most recent fiscal year, along with the standard disclosure that higher turnover may indicate higher transaction costs and tax consequences.1Securities and Exchange Commission. FORM N-1A
To see turnover over time, open the Financial Highlights table in the fund’s annual or semi-annual shareholder report. That table covers the past five years, or since inception for newer funds, and lists turnover next to expense ratios, per-share income, and total return.2SEC.gov. How to Read a Mutual Fund Shareholder Report The raw purchase and sale figures that feed the numerator appear in the Statement of Changes in Net Assets or in the notes to the financial statements. The monthly portfolio valuations behind the denominator are calculated internally and aren’t always broken out line by line, which is why most investors work from the reported percentage rather than reconstructing it.
Reading What the Rate Actually Means
A turnover figure only tells you something when you have a baseline. The S&P 500 index itself turns over roughly 3% per year on average, which sets a floor for funds that passively track it.3S&P Global. Index Dashboard: S&P 500 Factor Indices After investor cash flows and small rebalancing trades, a well-run S&P 500 index fund typically reports single-digit turnover.
Actively managed equity funds run higher. Rates in the 40% to 80% range are common, and aggressive strategies can push past 100%. A rate above 100% doesn’t mean the fund held nothing for a full year; it means the dollar volume of trading exceeded the average portfolio value. Volatile markets also lift turnover regardless of strategy. When rates move suddenly or a sector’s earnings collapse, even disciplined managers may rebalance more than usual, so a single spike doesn’t always signal a change in philosophy. Comparing three to five years of turnover shows whether heavy trading is the design or a response to conditions.
What High Turnover Costs You
Two costs sit behind the number: taxes and trading.
Every time a fund sells a security at a profit, it generates a capital gain, and funds are required to distribute those gains to shareholders, typically at year-end. If you hold the fund in a taxable brokerage account, you owe tax on the distributions whether you reinvested them or not. Securities the fund held less than twelve months produce short-term capital gains, taxed at your ordinary income rate, which for 2026 can run as high as 37%. Securities held longer produce long-term capital gains, taxed at 0%, 15%, or 20% depending on your taxable income.
High-turnover funds tend to generate more short-term gains because they trade within months. That’s the worst tax outcome: your top rate applied to gains you didn’t choose to realize. Low-turnover funds hold long enough to qualify for the lower long-term rates and distribute fewer gains overall. None of this matters inside a 401(k) or IRA, where distributions aren’t taxed until withdrawal. In a taxable account, the gap between a 15% turnover fund and a 150% turnover fund can meaningfully reduce after-tax return.
The second cost is trading itself. Brokerage commissions and bid-ask spreads don’t show up in the expense ratio. Prospectuses are required to disclose that transaction costs from portfolio turnover are not reflected in annual fund operating expenses but still affect performance.4SEC.gov. Fees and Expenses – Global X U.S. 500 ETF Prospectus Research on U.S. equity funds has found that each 100 percentage points of turnover reduced annual returns by roughly 0.4% for large-cap funds and more than 0.5% for mid- and small-cap funds. International stock funds fared worst, losing nearly 0.9% per 100 points of turnover. A fund with 100% turnover has to beat its benchmark by enough to cover that drag before its shareholders see any advantage.