Strike price and expiration: how to read an option chain — options trading, chapter 3

The standard belief is that picking an option means picking a direction — bullish, buy a call; bearish, buy a put. That's the easy half. The hard half, and the one that actually decides whether you make money, is picking the strike and the expiration. Two traders can be equally right about direction and one profits while the other loses the premium, purely because they chose different strikes and dates.

Chapter 2 covered the four positions assuming a fixed strike and a fixed expiration. This chapter is about those two coordinates: what they are, the menu of choices, the rules that govern when and how a contract settles, and how to read the grid where all of it is listed — the option chain.

The strike is the fixed transaction price

The strike (or strike price, or exercise price) is the price written into the contract at which you can buy (call) or sell (put). It does not change. A $100 call lets you buy at $100 whether the stock is at $90 or $150.

For any given stock, the exchange lists many strikes spaced around the current price — often every $1, $2.50, or $5 depending on the stock's price and liquidity. So if $AAPL trades at $100, you'll see calls and puts at $90, $95, $100, $105, $110 and beyond. The strike you pick relative to the current price determines the option's "moneyness" — how much of the premium is real value versus pure time bet — which is the subject of the next chapter.

Expiration: weeklies, monthlies, and LEAPS

Expiration is the deadline. After it, the contract is gone — settled or worthless. Listed equity options come in three rough buckets by tenor.

• Weeklies expire on Fridays, week after week. They're cheap (little time left) but the time value bleeds out fast.
• Monthlies are the standard, oldest series: they expire on the third Friday of each month. Most quoted open interest and the deepest liquidity historically cluster here.
• LEAPS (Long-term Equity AnticiPation Securities) are long-dated options, expiring more than a year out. They cost much more in absolute terms but decay slowly, which is why they're used as lower-capital, longer-horizon stock proxies.

The further out the expiration, the more you pay — you're buying more time for your thesis to play out. The trade-off is direct: nearer expiry is cheaper but punishes you faster if the move doesn't come; further expiry costs more but buys patience.

Standardized and cleared by the OCC

You don't negotiate these contracts with a counterparty. Listed options are standardized — fixed 100-share multiplier, fixed strikes, fixed expiration dates — and centrally cleared by the Options Clearing Corporation (OCC), which stands between buyer and seller and guarantees the contract. That's why you can sell an option you bought to a completely different trader: every $100 AAPL monthly call is identical and fungible. Standardization plus central clearing is what turns options from bespoke agreements into a liquid market.

American vs European exercise

Two exercise styles exist, and the difference matters for assignment risk.

• American-style options can be exercised any time up to and including expiration. US single-stock options are American. That means if you've sold one, you can be assigned early — at any point before expiry — most commonly around dividend dates.
• European-style options can be exercised only at expiration. Many cash-settled index options, such as those on the S&P 500 index (SPX), are European. No early assignment.

The label has nothing to do with geography — both styles trade on US exchanges. It's purely about when the holder can pull the trigger.

Settlement: shares vs cash

What you actually receive when an option is exercised depends on the underlying.

• Equity options settle physically — in shares. Exercise a single-stock call and 100 shares are delivered to your account (and the cash debited); exercise a put and your shares are sold at the strike. Get assigned on a short put and 100 shares land in your account at the strike, requiring real cash.
• Index options settle in cash. There are no "shares of the S&P 500 index" to deliver, so the contract pays out the cash difference between the index level and the strike. SPX is the canonical example.

If you don't want to wake up to 100 shares (or owe for them), you generally close the position before expiration by trading out of it — far more common than actually exercising. Most options are closed, not exercised.

Choosing strike and expiration: the trade-offs

The two coordinates interact, and every choice is a cost-versus-probability trade.

• Nearer expiration = cheaper, but faster time decay. You pay less, but the option loses value quickly as the days run out. A few quiet sessions can erase a near-dated option even if you're eventually right.
• Further-out-of-the-money strike = cheaper, but lower probability of paying off. A strike far from the current price costs little because it's unlikely to get there. The lottery-ticket archetype — a far-OTM weekly — is cheap precisely because it usually expires worthless.

There's no universally "best" choice; there's only the one that fits your thesis, your timeframe, and your position sizing. Closer strikes and longer dates cost more but are more forgiving. The next chapter makes this concrete by splitting the premium into the part you're paying for real value and the part you're paying for time.

How to read an option chain

The option chain is the grid your broker shows for a given expiration. The standard layout:

• Strikes run down the middle, from low to high.
• Calls on one side, puts on the other — conventionally calls on the left, puts on the right.
• Each row shows bid (what buyers will pay) and ask (what sellers want); you buy near the ask, sell near the bid, and the gap between them is the spread — wider spreads mean worse fills and thinner liquidity.
• Volume is contracts traded today; open interest is the total contracts outstanding. Both gauge liquidity — high numbers mean tighter spreads and easier exits.

You pick a chain by choosing an expiration (usually a tab or dropdown), then scan the strikes for the one matching your view, checking the bid/ask spread and open interest before committing. On a broker like IBKR, the chain is the launch pad for every options order — and the order-type discipline from the stock course applies: use limit orders on wide spreads, never market orders into thin chains.

What to watch when choosing strikes and dates

• The bid/ask spread. A $0.50-wide spread on a $2.00 option is a 25% round-trip cost before the stock moves an inch. Thin chains quietly tax every trade — check the spread first.
• Open interest and volume. Low numbers mean you may not be able to exit at a fair price. Liquidity is a feature, not a detail.
• Early-assignment risk on American options. If you're short a single-stock option, dividends and deep-in-the-money strikes raise the odds of being assigned before expiration. Know the ex-dividend date.
• Settlement type. Equity = shares delivered; index = cash. Don't get surprised by 100 shares — or by a contract that can't deliver shares at all.
• Matching tenor to thesis. A multi-month thesis on a weekly option is a bet against the clock. Buy enough time for the move you actually expect.

---

Next in this series: Option premium: intrinsic vs extrinsic value — what you're actually paying for, split in two.

See it live: explore liquid optionable tickers on /stocks; trade the chain through /stack/ibkr.

QuantAbundancia is educational research. Nothing here is investment advice. See /disclosures.