Delta

Delta is one of the options Greeks — it measures how much an option's price should move for a $1 move in the stock. A call with a delta of 0.50 should gain roughly $0.50 for every $1 the stock rises; a put's delta is negative, since puts gain value as the stock falls. Traders also read delta informally as a rough odds estimate (a 0.30 delta as roughly a 30% chance of finishing in-the-money) and as a hedge ratio describing how many shares an option position behaves like. Delta isn't fixed — it moves toward 1.0 (or -1.0 for puts) as an option goes deeper in-the-money, and toward 0 as it moves further out-of-the-money.