Options Greeks Explained in Plain English

The Greeks are four numbers that measure how an option's price changes in response to different market forces. Understanding them transforms options from a guessing game into a quantifiable, manageable trade.

Delta — Directional Exposure

Delta tells you how much the option price moves per $1 move in the underlying stock. A call with 0.30 delta gains $0.30 when the stock rises $1. A put with -0.30 delta gains $0.30 when the stock drops $1. Delta also approximates the probability of expiring in-the-money: a 0.30 delta call has roughly a 30% chance of being ITM at expiration. For premium sellers, delta determines your directional risk — selling a 0.20 delta put gives you an 80% probability of keeping the full premium.

Gamma — The Accelerator

Gamma measures how fast delta changes as the stock moves. It's highest for at-the-money options near expiration. Gamma is dangerous for sellers because it means your directional exposure can shift rapidly against you. A short put with 0.10 delta might seem safe, but if the stock drops sharply, gamma accelerates delta toward 0.50 or higher — suddenly you have much more risk than you planned for. This "gamma risk" is why experienced sellers avoid short-dated ATM options.

Theta — Time Decay (The Seller's Edge)

Theta is how much value an option loses each day just from the passage of time. A theta of -0.05 means the option loses $5 per contract per day. For buyers, theta is the enemy — your position bleeds value every day you hold it. For sellers, theta is the engine of income — every day that passes transfers value from the buyer to you. Theta accelerates sharply inside 30 days to expiration, which is why the 20-45 DTE window is the sweet spot for premium sellers.

Vega — Volatility Sensitivity

Vega measures how much the option price changes per 1% change in implied volatility. If an option has a vega of 0.15, a 1% increase in IV adds $15 per contract. This is critical for premium sellers: when you sell options during high IV, you're collecting inflated premium. When IV drops (as it usually does after fear events or earnings), vega works in your favor as the option you sold loses value from the IV contraction.

You can't manage what you don't measure. The Greeks turn abstract risk into concrete numbers that inform every decision — from strike selection to position sizing to trade management.

Delta for Position Construction

When selling puts, your delta choice directly controls your risk-reward balance. A 0.30 delta put collects more premium but has a 30% chance of assignment. A 0.15 delta put collects less but has only a 15% chance. Flow Proof's scanner adjusts target delta based on the VIX regime: tighter deltas in calm markets (0.25-0.35), wider deltas in volatile markets (0.15-0.20) where rich premium makes further OTM strikes worthwhile.

Theta for Expiration Selection

Understanding theta's acceleration curve lets you pick the optimal expiration. Selling 45 DTE gives you the best balance of total premium and daily decay rate. Selling 7 DTE captures the fastest decay but exposes you to maximum gamma risk. The math is clear: 30-45 DTE maximizes time decay per unit of gamma risk.

Vega for Timing Entries

IV Rank tells you whether premium is historically rich. Vega tells you exactly how much that richness is worth in dollar terms. When IV Rank is 80 and vega is high, selling options locks in premium that will shrink as IV reverts to the mean — a double edge of theta decay plus IV contraction.

How the Greeks Interact

The Greeks don't operate independently. Near expiration, gamma spikes while theta accelerates — creating a high-reward but high-risk environment. During IV crushes, vega drives rapid price changes that can overwhelm theta's steady decay. Understanding these interactions prevents surprises and helps you construct positions that profit from the Greeks you want while minimizing exposure to the ones you don't.

Flow Proof integrates Greeks into every layer of the platform — from the scanner's delta targeting to the AI trade card's strike recommendations.

VIX-Adaptive Delta Targeting

The market regime dashboard classifies VIX into five regimes (Low, Normal, Elevated, High, Extreme) and automatically adjusts the recommended delta for put selling. In a Low VIX environment, the target delta is 0.35 (closer to ATM for meaningful premium). In Extreme VIX, the target drops to 0.15 (further OTM where rich premium still generates income with a wide safety margin). This ensures your Greek exposure adapts to market conditions.

Theta in the AI Trade Card

Every AI-generated trade recommendation shows the daily theta for the recommended position. You can see exactly how much time value you collect per day — making it easy to compare opportunities across different symbols and expirations. A put on COIN collecting $4.20/day in theta vs a put on AAPL collecting $1.80/day gives you a concrete basis for allocation decisions.

Greeks-Informed Strike Selection

The AI analysis selects strikes where the Greek profile favors the premium seller: delta in the target range for the current VIX regime, theta near the steepest part of the decay curve, and gamma low enough that a 2-3% adverse move doesn't dramatically shift your risk profile. This Greek-aware approach produces more consistent outcomes than simply selling "the highest premium" strike.