Strike, Expiry and the Shape of the Chain

The fields that change the position

A chain looks like a wall of numbers and it is really six decisions. The strike sets where intrinsic value begins, and therefore how much of the premium is a claim on the move; the expiry sets how much time is packaged in the contract; the type decides the direction of the right; the multiplier converts a per-share quote into the dollars that will actually change hands; the trading style decides whether an American contract can be exercised early; and the bid-ask is what the position costs to enter and leave. Only the first three are usually discussed, which is why learners are surprised by the last one — the spread is a certain cost and the move is an uncertain benefit, and on a wide quote the certain cost can exceed the expected benefit entirely. Two fields are widely misread. Volume and open interest both describe how many contracts have changed hands or remain open, and neither is a direction signal: a large open interest means many participants hold positions at that strike, which is a liquidity fact and occasionally a level-of-interest fact, and it says nothing about which way they are positioned without knowing whether they are long or short. The second is implied volatility, which appears on most chains as a number beside each strike and is the market’s price for movement rather than a forecast. Reading a chain well means knowing which of the columns is a decision, which is information about liquidity, and which is a price for uncertainty — because the same number can be all three to different people. From quote to position — Quote $2.40 per share: $240 a contract at a multiplier of 100 · Bid $2.30, ask $2.60: Round trip costs $0.30 a share = $30 a contract before any move ← · Ten contracts: $2,400 of capital for the same exposure scaled tenfold · Strike and expiry choice: Sets the intrinsic-extrinsic split and the time available ← A practical screen for liquidity: if the bid-ask is more than a couple of percent of the contract’s mid price, the position will be expensive to hold, and the arithmetic of the strategy has to clear that cost before it clears anything else.

Multiplier, settlement, and the two ways to be wrong about units

The multiplier is where arithmetic errors become expensive. A quoted premium is per share, a contract covers a hundred shares, so a $0.45 quote is $45 and a five-contract position is $225. Getting this wrong in the direction of thinking in shares tends to understate capital at risk by a factor of a hundred; getting it wrong the other way — treating the premium as the total outlay — overstates it. Both errors are common enough that the habit worth building is to write the dollar figure down before the decision: premium × 100 × contracts, on the page, every time. Settlement has a similar quality: it rarely matters until the moment it does. Equity options are physically settled against the underlying when exercised, which is why a covered call can result in shares being called away and a short put can result in shares arriving in the account. Index options in many cases settle in cash, which is why a trader who has been trading equity options can be surprised by the mechanics elsewhere. The practical point is not the detail but the timing: assignment and exercise decisions arrive at expiry, so the position that is fine on Thursday can become a stock position on Saturday — and the plan should say in advance whether that is acceptable. • Strike: where intrinsic value begins, and therefore the exposure to the move. • Expiry: the amount of time packaged into the contract. • Multiplier: 100 shares per contract, the source of most unit errors. • Bid-ask: a certain cost paid on both sides of a round trip. • Open interest: a liquidity fact, not a direction signal. • Settlement: physical for equity options, so assignment means delivery. Both legs of a spread have their own spread. A two-leg position pays the bid-ask twice, once on each contract, so the cost of a vertical is roughly double the cost of a single leg and the arithmetic of the strategy has to clear that. A quoted mid price for a spread is a hope rather than a fill.

The expiry date is not one date, it is a schedule

The expiry printed on a chain is one row of a calendar, and where it sits changes the trade. Standard equity options expire on the third Friday of the month, and quarterly expiries — March, June, September, December — are the ones the largest contracts and the index products list. Most large names also list weeklies every Friday, and the shortest-dated of those now carry a large share of all option volume on the busiest names. Two facts follow for anyone reading a chain. First, **the nearest expiry has the tightest absolute spreads and the worst relative ones**: a 10-cent-wide quote on a 30-cent option is a 33% round-trip cost, which is why short-dated contracts are cheap per contract and expensive per unit of risk. Second, the standard expiries carry real size while far weeklies and far monthlies can be nearly empty, so the contract with the best-looking price is often the one nobody is trading. Check open interest and the width of the quote before you check the price. One more consequence worth knowing before it costs you: an option that expires worthless is a closed position the broker has to remove, and a contract left to expire is not the same as one you closed. Margins, assignment and the weekend all happen on the exchange’s schedule, not yours.

The contracts that stop being standard

The 100-share multiplier is the default, not a law. When a company does something to its own capital structure, the OCC adjusts the outstanding series so that the economic terms are preserved, and the result is a contract whose deliverable is no longer a round hundred shares. A **two-for-one split** halves the strikes and doubles the multiplier, so one contract controls two hundred shares — which is why a chain viewed in the week before a split shows a mixture of old and new strikes that look like misprints. A **special cash dividend** large enough to be treated as a return of capital can produce a contract that delivers 100 shares plus a cash amount, and a **merger** can leave the deliverable as cash, or shares of the acquirer, or a combination of both. Adjusted contracts are a real trap for anyone doing the arithmetic in the first lesson. The per-share premium you read on the screen still means what it says, but the dollars it becomes depend on a multiplier you have to look up rather than assume, and the strike price may not correspond to any round number a share price could reach. Worse, the market in an adjusted series is usually thin: most participants move to standard contracts on the new terms, spreads widen, and a position that looked easy to close becomes an order that has to be worked. The practical rules are short. Never assume the multiplier; read it from the chain. Treat any position held across a corporate action as a position that has changed, and re-read its terms after the event rather than reconciling the difference as a pricing error. And when a covered call is written on a position that is about to be adjusted, check what the writer is actually obliged to deliver, because it may not be the 100 shares they believe they own. • Splits adjust strikes and multiply the deliverable; a 2-for-1 turns 100 shares into 200. • Special dividends and spin-offs can add a cash component to the deliverable. • Mergers can change the deliverable to cash or another company’s shares. • Adjusted series are thinly traded, so the round-trip cost is higher than the standard contract’s quote suggests. The multiplier is a field on the contract, not an assumption. A price of $3.20 is $320 for a standard contract and could be $480 for one adjusted by a three-for-two split — a fifty percent error introduced by a default that is almost always right.

The identifier: how a contract is named

An option contract is identified by a symbol that encodes everything a holder needs to know, and reading that string is a small skill that prevents a specific and expensive class of mistake — trading the wrong series in a chain that has several that look alike. The traditional symbol has four parts. The **root** identifies the underlying, and it can change when a company reorganises or a ticker is reused. The **expiry** is encoded as a date, which places the contract in a cycle. The **strike** is encoded as a letter code together with a strike-price field, which is the part that produces the confusion: the letter maps to a price within a range that resets over time, so the same letter can mean different strikes in different periods, and older reference tables go stale. And the **type** distinguishes a call from a put. Modern venues and data providers use longer identifiers that spell the strike out, which removes the ambiguity but is not what every platform displays. The practical consequence is that a chain can contain series that differ in a way the eye skips. Two contracts on the same underlying with the same displayed strike can be different expiries a week apart; a weekly and a monthly can sit next to each other with nearly identical prices. And after a corporate action, the picture changes more fundamentally: the exchange’s clearing house adjusts the contract rather than replacing it, so the deliverable behind an old series may no longer be a round number of shares. The usual approach is to keep the strike and the expiry and change the number of shares or the cash component delivered, which produces values like a multiplier of one hundred and a deliverable of seventy-three shares and some cash. A contract that used to be comparable with its neighbours becomes a bespoke instrument, and the pricing conventions around it — the tick size, the liquidity, the implied volatility the market quotes — become unreliable. That is why the field to check first on any unfamiliar contract is not the price but the **deliverable**. A series whose multiplier or share count is not the standard one is not merely less liquid; it is a different instrument, with its own volatility and its own pricing behaviour, and often with a spread wide enough that entering or leaving costs more than the mispricing that made it look appealing. Selling an adjusted contract to somebody who has not noticed the deliverable is a recognisable and unpleasant experience. The habits that prevent all of this are unglamorous: confirm the underlying, the expiry date and the deliverable before the strike is even considered, and be suspicious of any series whose spread is unusually wide compared with its neighbours in the same chain. A wide spread in an otherwise liquid chain is usually a signal, and the signal is that the contract is not the one you think it is. • The symbol encodes root, expiry, strike and type, and the strike letter can mislead. • Weekly and monthly expiries sit beside each other in a chain and look nearly identical. • After a corporate action the deliverable changes while the strike and expiry stay. • Check the deliverable first, and treat an unusually wide spread as a signal. One habit that catches most of it: paste the contract symbol into a search rather than reading it off the platform. A definitive description of the terms takes a few seconds and is the difference between trading the series you intended and one that merely had the same strike.

Sources

• Option chain fields and conventionsCBOE educational materials
• Bid-ask spreads and option transaction costsMarket microstructure literature on listed option liquidity
• Open interest and volume interpretationOptions Clearing Corporation educational publications