SPX is the commonly used symbol for the S&P 500 Index, which measures the performance of large-cap U.S. equities. It is the underlying index at the center of SPX Gamma’s market analysis and trading frameworks.
The S&P 500 uses float-adjusted market-capitalization weighting. A company’s weight reflects its market value adjusted for the shares available for public trading. Larger constituent companies generally have greater influence on index movements.
No. SPX reflects the weighted performance of its constituents. Gains in heavily weighted companies can outweigh declines elsewhere, so a rising index does not mean every constituent—or every stock in the broader market—is rising.
SPX options have a $100 multiplier. One option point represents $100 per contract, so an option quoted at 5.00 points has a premium value of $500 per contract before fees.
SPX options are cash-settled. At expiration, an in-the-money contract settles through a cash payment based on its settlement value rather than delivery of shares. European-style exercise means the option can be exercised only at expiration; it does not prevent traders from closing a position before the applicable trading cutoff.
AM-settled contracts use a settlement value calculated from the opening prices of constituent stocks. PM-settled contracts use a settlement value based on closing prices. SPXW identifies PM-settled SPX options. The settlement method affects when the final value is determined and the price exposure a position carries into expiration.
Trading cutoffs and settlement timing differ by contract. Traders should verify the specific expiration, settlement method, and last trading time before entering a position. These mechanics provide the foundation for understanding SPX option flow, gamma exposure, volatility, and trading strategies.