In March 2026, about 17.4% of SPX options volume traded through open outcry on Cboe’s physical floor: 937,000 contracts of average daily volume (ADV), out of 5.4 million total SPX contracts ADV. That is roughly one contract in six for that month—not a fixed share of SPX activity. And “flow” volume does not, by itself, tell you whether traders were bullish, bearish, hedging, opening positions, or closing them.
How much SPX options volume trades on the physical floor?
Cboe’s March 2026 volume report gives both figures needed for a same-period comparison: 937,000 SPX contracts of open-outcry ADV and 5.4 million SPX contracts of total ADV. Dividing the floor figure by the total gives about 17.4%, or roughly one in six contracts. The percentage is calculated from Cboe’s reported averages; it is not a fixed market share and should not be carried over to other months without matching venue data. Cboe’s March 2026 volume report
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The floor is one execution venue within a much larger market. Cboe’s description of its Chicago trading floor identifies an SPX options pit, while the exchange also supports electronic trading. Open-outcry volume is therefore a meaningful part of activity, but it is not a description of all SPX trading.
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Open outcry is a human, in-person method of arranging trades in a trading pit. Cboe says customers continue to value it especially for larger, more complex orders, price discovery, and liquidity provided by market-makers and floor brokers. That is the exchange’s explanation of the floor’s role—not evidence that every floor trade is large or complex. Cboe’s announcement about its Chicago trading floor
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The contrast is not simply “floor or no trading.” SPX options can also trade electronically, and Cboe lists sessions that are entirely electronic. The venue can matter to how an order is executed, but a venue label alone does not disclose the trader’s purpose or the position’s risk.
How large is SPX options activity overall?
SPX volume is substantial, and the reported figures vary by period and measure. Cboe reported 3.9 million SPX contracts of ADV for 2025; 2.3 million of those were 0DTE contracts, or 59% of the total. In the second quarter of 2026, Cboe reported quarterly SPX ADV of 5.1 million contracts. It also reported a single-day record of 7.8 million contracts traded on June 5, 2026, described as a record at that time. These yearly, quarterly, and daily numbers are not interchangeable. Cboe’s 2025 options-industry report and Cboe’s June 2026 volume report
What “flow” volume can—and cannot—tell you
A volume print counts contracts traded. It does not identify a participant’s conviction or explain the full strategy around a trade. A transaction necessarily has a buyer and a seller, but the print alone does not show whether either party initiated a new position or offset an existing one. It also cannot establish that one side was making a directional bet rather than hedging or trading as one leg of a broader position.
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For that reason, “SPX flow” is best treated as a description of observed trading activity, not a direct readout of trader intent. Venue-level totals can tell you how much activity was recorded on the floor for a specified period; they cannot, by themselves, tell you what the participants expected the index to do.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Which SPX trading sessions are electronic?
Cboe lists regular, curb, and global trading hours for SPX options. Its hours page identifies the global trading hours (GTH) and curb sessions as all-electronic. The product specification snapshot dated March 19, 2024 lists regular trading from 9:30 a.m. to 4:15 p.m. ET, curb trading from 4:15 p.m. to 5:00 p.m. ET, and GTH from 8:15 p.m. to 9:25 a.m. ET. Because that specification is dated, check Cboe’s current schedule before relying on the hours or contract details for a live trade. Cboe hours and holidays and Cboe SPX options product specifications
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