Reading the Options Chain

What the chain shows

An options chain is a table. It lists every option available on a single underlying for a single expiry, sorted by strike price. Calls are typically on the left, puts on the right, and the strike runs down the middle. Spot price (where the underlying is trading right now) anchors the at-the-money row.

Every broker arranges the chain a little differently, but the columns you actually need are always there: bid, ask, last price, implied volatility, volume, and open interest.

Bid and ask

The bid is the highest price someone is willing to pay for the option right now. The ask is the lowest price someone is willing to sell it for. The difference is the spread. You generally pay the ask when you buy, and receive the bid when you sell.

On liquid names like SPY or QQQ at near-the-money strikes, the spread can be one or two cents. On illiquid names or far-out-of-the-money strikes, it can be twenty cents or more. A wide spread is a tax on every entry and every exit. It is the single most common reason a strategy that looks profitable on paper loses money in practice.

Strike, in-the-money, out-of-the-money

The strike is the price at which the option can be exercised. Relative to spot, every option is in one of three states:

• In the money (ITM): a call with a strike below spot, or a put with a strike above spot. The option already has intrinsic value.
• At the money (ATM): strike approximately equal to spot. Most of the price is time value, none is intrinsic.
• Out of the money (OTM): a call above spot, or a put below spot. The option is entirely time value. It pays nothing if exercised today.

Most volume on most days is concentrated near the at-the-money strikes. That is where the most useful information lives, because that is where the market is making active bets.

Implied volatility

The IV column is the most important number on the chain. IV is the market's estimate of how much the underlying will move (in annualized percentage terms) between now and expiry. A SPY ATM IV of 14% means the market is pricing in roughly 14% annualized realized volatility over the option's life.

IV is what you are really buying or selling when you trade an option. The directional view (call or put, up or down) gets the headline, but the actual price you pay is determined almost entirely by IV. This is why two calls with the same strike on the same stock can cost wildly different amounts on different days even if the stock has not moved.

Lessons L.10 and L.11 cover IV in depth. For now, treat it as the single most informative number on the chain.

Volume and open interest

Volume is the number of contracts traded today. Open interest is the number of contracts outstanding (not yet closed or expired). Volume tells you what is happening today. Open interest tells you where positions have built up over time.

Both matter for liquidity. A strike with no volume and no open interest is a strike where you might not be able to exit a position cleanly. Stick to liquid strikes when you are starting out. The bid-ask spread will tell you the same story, but volume and open interest confirm it.

What changes day to day

Strikes are fixed. Expiries are fixed. What moves is the spot price (which shifts which strike is ATM), the bid-ask spreads, the implied volatilities, and the volume. A trader who reads the chain every day starts to see patterns: where IV usually sits, where it spikes before earnings, which strikes attract steady flow.

A trader who only looks at price misses everything happening underneath.

What you carry forward

• Bid is what buyers will pay; ask is what sellers will accept. The difference is the spread.
• ITM, ATM, and OTM describe the strike's relationship to spot.
• Implied volatility is the most informative single number on the chain.
• Volume and open interest tell you about liquidity and positioning history.
• Always check spot, ATM IV, and spread before doing anything else.