Skew is the relative richness of put vs call options, expressed in terms of Implied Volatility (IV). For options with a specific expiry, 25 Delta Skew refers to puts with a delta of -25% and calls with a delta of 25% to demonstrate this difference in the market’s perception of implied volatility. 25 Delta Skew is calculated as the difference between a 25-delta put’s implied volatility and a 25-delta call’s implied volatility, normalized by the ATM Implied Volatility. This metrics focuses on option contracts expiring in 1 month.

This is the Point-in-Time (PiT) variant of 25 Delta Skew Normalized (1 Month). PiT metrics are strictly append-only and their history is immutable. The historic data does not necessarily reflect the best current knowledge, but the information at the time when a data point was first computed. PiT metrics are ideal candidates for applications in model backtesting and related quantitative purposes. Read our article on PiT metrics for more information.