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20 Delta vs. 30 Delta Short Puts: Risk, Premium
Choosing between a 20-delta and 30-delta put is not a search for a magic number. It is a portfolio decision about how much premium, directional exposure and assignment risk you are willing to accept.
What delta is actually telling you
Delta is primarily a sensitivity measure: it estimates how much an option price may change for a $1 move in the underlying, all else equal. Traders also use delta as a rough probability proxy, but it is not a literal promise that a 20-delta option has exactly a 20% chance of assignment. Delta changes as price, time and implied volatility change.
The practical difference between 20 and 30 delta
A 30-delta put generally starts closer to the stock price than a 20-delta put with the same expiration. The closer strike normally collects more premium, but it also starts with more downside sensitivity and less distance before the strike is challenged. The 20-delta put usually gives up some credit in exchange for more room.
When a higher delta can make sense
A higher-delta put can fit an investor who genuinely wants to buy the shares at the strike and has already budgeted for assignment. In that case, premium is secondary to the purchase price and portfolio fit. The position should still be sized for a large stock decline, not for the premium received.
When a lower delta can make sense
A lower-delta strike may fit an income-oriented seller who values a larger initial buffer and is willing to accept a smaller credit. Lower delta does not make a put safe. A major gap or market selloff can move through several strikes quickly.
Delta and DTE must be considered together
A delta number cannot be separated from time to expiration. A 30-delta option with a week left can behave very differently from a 30-delta option with six weeks left because gamma, theta and event exposure differ. Strike selection should therefore be made with DTE, volatility, earnings and portfolio concentration in view.
A better decision rule
Start with the price at which you would actually accept the stock obligation. Then check the delta and premium. If the strike is unattractive as a stock purchase, a richer credit does not repair the trade. If assignment would create a concentration or liquidity problem, the position is too aggressive regardless of delta.
Use the free Options Seller's Risk Checklist
Before selling premium, define the underlying, event risk, assignment plan, portfolio impact and exit rules.
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Selling Puts · Delta & Strike Selection · Options Trading Plan