Delta
An option Greek measuring price sensitivity to a 1-point move in the underlying — and a fast approximation of the probability of finishing in the money.
Delta is one of the option ‘Greeks.’ It measures how much an option's price is expected to change for a 1-point move in the underlying, and it doubles as a fast approximation of the probability that the option finishes in the money.
Two ways traders use delta:
- ●As sensitivity: a 0.40 delta Call gains about $0.40 (before the contract multiplier) for each 1-point rise in the underlying.
- ●As probability: a 20-delta short strike has roughly a 20% chance of finishing in the money — about an 80% chance of expiring worthless — handy for picking Credit Spread and Iron Condor strikes.
The catch — delta drifts. It changes with every move in price and every shift in implied volatility, so a ‘20-delta’ strike this morning is a different distance from spot by the afternoon. That is why disciplined traders also anchor strikes to standard deviations (sigma) off the expected move, a measure that does not drift the way raw delta does.
Common calibrations in the playbook: 10–20 delta short strikes for Credit Spreads (65–70%+ probability of profit), and 15–20 delta for multi-day Iron Condors.
How SPXXL helps: the expected-move rails translate delta-style strike selection into concrete sigma distances on the chart, so your strikes line up with real probability.
Related Terms
The estimated chance a trade is profitable at expiration — the most useful single number for comparing premium-selling trades before entry.
The statistical measure of expected price travel — the backbone of sigma-anchored strike selection that converts implied volatility into a distance on the chart.
The options-implied price range SPX is expected to stay within by the close — derived from ATM implied volatility using the 1-standard-deviation (68%) probability envelope.
A two-leg, defined-risk structure: sell a nearer option and buy a further one for protection, collecting a net credit — the workhorse of high-probability premium selling.
A four-leg credit spread that profits when price stays within a defined range — ideal for Balanced Day and Volatility Compression sessions.
The aggregate Gamma positioning of options market makers — determines how dealer hedging amplifies or dampens SPX price moves.