What is delta? The greek that tracks price moves

Delta is the first and most-used option greek. It tells you approximately how much an option's price changes when the underlying stock moves by $1. A delta of 0.30 means the option gains about $0.30 if the stock rises $1 — and loses about that much if it falls.

Geometrically, delta is the slope of the curve that plots option price against stock price. A steeper slope means the option tracks the stock more closely.

Call deltas run from 0 to 1; put deltas run from -1 to 0, because puts gain value as the stock falls. Traders often drop the decimal and say a '30-delta' option, meaning 0.30.

An at-the-money option sits near 0.50 delta. Deep in-the-money options approach 1.00 and behave almost like the stock itself; far out-of-the-money options approach 0 and barely move.

Delta doubles as a quick estimate of the chance the option finishes in the money at expiration. A 0.30-delta call has roughly a 30% chance of expiring ITM.

It is an approximation, not a guarantee, but it is a handy way to compare strikes at a glance.

Because one contract controls 100 shares, delta also tells you your share-equivalent exposure. A 0.30-delta call behaves like owning about 30 shares (0.30 × 100).

This 'hedge ratio' view is why delta is central to managing risk across a whole position.

When you sell cash-secured puts, the put's delta is a shorthand for assignment odds. Selling a 0.30-delta put means roughly a 30% chance of being assigned — and usually more premium than a lower-delta strike.

Choosing a delta is really choosing a trade-off between premium collected and how often you take assignment. New to that flow? See the Wheel strategy basics and Options 101 lessons.