Learn/The Greeks That Matter/Lesson 1
Lesson 1 of 5

Delta -- Your Probability Compass

What Is Delta?

Delta measures how much an option's price changes for every $1 move in the underlying stock. But for wheel traders, delta's real power is its second interpretation: it approximates the probability that the option will expire in the money (ITM). A put with a delta of -0.20 has roughly a 20% chance of finishing ITM -- meaning an 80% chance your cash-secured put expires worthless and you keep the full premium.

Delta range
Calls: 0 to +1.0 | Puts: 0 to -1.0 | |Delta| ~ P(ITM)

Delta as a Probability Estimate

When you sell a 0.30-delta put, the market is pricing roughly a 30% probability that the stock will fall below your strike by expiration. That means there is about a 70% chance you simply collect the premium without being assigned. This probability lens is how experienced wheel traders choose their strikes -- they pick a delta that matches their comfort level with assignment risk.

Lower Delta (0.10-0.20)
  • +Higher probability of expiring OTM (~80-90%)
  • +Smaller premium collected
  • +Wider margin of safety
  • +Best for conservative wheel traders
Higher Delta (0.30-0.40)
  • –Lower probability of expiring OTM (~60-70%)
  • –Larger premium collected
  • –Smaller margin of safety
  • –Best for income-focused traders willing to own shares

How Delta Changes with Stock Price

Delta is not static. As the stock price moves toward your strike, delta increases (gets closer to -1.0 for puts), signaling that assignment is becoming more likely. Conversely, if the stock moves away from your strike, delta shrinks. This is why monitoring delta after opening a trade is just as important as choosing it initially.

The Wheel Trader's Sweet Spot
Most successful wheel traders sell puts at 0.20 to 0.30 delta. This range balances meaningful premium income with a comfortable probability of not being assigned. If you genuinely want to own the stock, you can go higher -- 0.35 to 0.40 delta -- to collect more premium at a strike closer to the current price.
Reading Delta in Practice
Stock XYZ trades at $100. The 30-DTE $90 put has a delta of -0.18 and costs $0.95. This tells you: (1) there is roughly an 82% chance the stock stays above $90, (2) for every $1 XYZ drops, this put gains about $0.18 in value, and (3) your breakeven if assigned is $89.05 ($90 - $0.95).
Key Takeaways
  • •Delta approximates the probability an option finishes in the money.
  • •Wheel traders typically sell puts at 0.20-0.30 delta to balance income and safety.
  • •Delta changes as the stock price moves -- keep monitoring after you open a trade.
Quick Check
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You sell a put with a delta of -0.25. Approximately what is the probability it expires out of the money?

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