Delta is a number between 0 and 1 that tells you two things at once: how much the option's price moves when the stock moves $1, and roughly the probability the option finishes in-the-money at expiration — closely related to strike price selection.
For covered call sellers, delta is the single most important number when choosing a strike. A 0.25 delta call has roughly a 25% chance of finishing in-the-money — meaning a 75% chance you keep your shares and the full premium.
What are delta's two meanings?
Price sensitivity
A 0.30 delta call moves $0.30 for every $1 the stock moves. If AAPL goes up $2, your call premium increases by about $0.60. As a seller, this means the option you sold is getting more expensive to buy back. This is where theta decay helps offset the move.
Probability proxy
A 0.30 delta means roughly a 30% chance the option finishes in-the-money. For you as a seller, that's a 70% chance the option expires worthless — which is exactly what you want. You keep your shares and the premium.
What delta should you use for covered calls?
Far out-of-the-money strikes. Very safe — you rarely get assigned. But the premium is modest. Best for stocks you really want to keep, or for your first few trades to build confidence.
The most popular range for covered call sellers. Meaningful premium with good odds. About 1 in 4 months you'll get assigned — but you sell at a profit. This is where most professionals operate.
Near-the-money or slightly out-of-the-money strikes. Maximum premium, but you'll get assigned roughly half the time. Best for stocks you'd be happy to sell at the strike price.
“Delta is the first Greek you should learn and the last one you should ignore. For covered call sellers, delta is your probability compass — it tells you the odds before you place the trade.”
— Common principle across options education (Tastytrade, Option Alpha)
What does delta look like in practice?
| Strike | Delta | Premium | Keep Shares | Style |
|---|---|---|---|---|
| $245 | 0.17 | $2.10 ($210) | ~83% | Conservative |
| $240 | 0.25 | $3.40 ($340) | ~75% | Moderate |
| $237.50 | 0.30 | $4.20 ($420) | ~70% | Moderate |
| $235 | 0.38 | $5.60 ($560) | ~62% | Aggressive |
| $232.50 | 0.45 | $6.80 ($680) | ~55% | Aggressive |
Notice the tradeoff: moving from the $245 to the $232.50 strike more than triples your premium ($210 → $680) but cuts your probability of keeping shares from 83% to 55%.
Rule of thumb
The screener shows “Chance OTM” which is simply 1 − delta. A 0.25 delta call shows as 75% Chance OTM. Focus on this number — it directly tells you the likelihood you keep your shares and the full premium. Combine this with IV Rank to time your entries.
Frequently asked questions
Does delta change over time?
Yes. As expiration approaches, delta moves toward 0 (if OTM) or 1 (if ITM). A 0.30 delta call that's still out-of-the-money with 5 DTE will have a delta closer to 0.10. This is good for sellers — it means your position is getting safer.
Is delta the same as probability of assignment?
It's a rough proxy, not an exact match. Delta is based on the Black-Scholes model and reflects risk-neutral probability. In practice, it's close enough to use as a probability guide. A 0.25 delta won't be exactly 25% assignment probability, but it's in the ballpark.
What about negative delta?
Puts have negative delta. A −0.30 delta put means the put gains $0.30 when the stock drops $1. For covered call sellers specifically, you're always looking at positive call delta.