How to read an option chain
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An option chain is the table of every listed option on one stock, arranged by expiration date and strike price, with the calls on one side and the puts on the other.
Key points
- Each row of an option chain is one strike price, and each expiration date has a table of its own.
- The bid is what a seller receives at once and the ask is what a buyer pays at once. The difference is a cost of trading.
- Volume counts the contracts traded today. Open interest counts the contracts that are open, and it is computed once a day after the close.
- The last price can be hours or days old. The bid and the ask say what the option trades at now.
On this page
An option chain is where an option is looked up before it is traded. Brokers and data sites draw it in slightly different ways, and its columns say the same things everywhere.
How an option chain is arranged
A chain belongs to one underlying stock. It is split by expiration date: one table for each date, the nearest first. Inside a table each row is a strike price, from the lowest to the highest. The calls are on one side of the strike price and the puts on the other.
The calls in the money are the ones with strike prices below the price of the stock, and the puts in the money the ones with strike prices above it. Options on stocks trade from 9:30 a.m. to 4:00 p.m. Eastern Time, and the quotes of a chain move during those hours.
What the columns of an option chain mean
| Column | What it says |
|---|---|
| Strike | The strike price of the row, per share |
| Bid | The highest price buyers offer now. A seller who trades at once receives it |
| Ask | The lowest price sellers ask now. A buyer who trades at once pays it |
| Bid size, ask size | The number of contracts offered at the bid and at the ask |
| Last | The price of the most recent trade, whenever that trade took place |
| Volume | The number of contracts traded today |
| Open interest | The number of contracts that are open, computed after the close of the day before |
| Implied volatility | The volatility that the premium implies, as a yearly percentage |
| Delta | The estimated change of the premium for a rise of $1 in the stock |
Every price in the chain is per share. One contract costs the quoted price times 100.
What the bid, the ask and the spread cost
The bid-ask spread is the ask less the bid. A buyer who pays the ask and sells at once at the bid loses the spread, so the spread is a cost that every round trip pays in one form or another.
The mid price, halfway between the bid and the ask, is an estimate of what the option is worth. It is not a price at which an order is sure to be filled.
A spread is judged against the premium. A spread of $0.05 on a premium of $2.00 is 2.5% of the price. A spread of $0.30 on a premium of $0.60 is half of it.
What volume and open interest say
Volume starts at zero every morning and counts every contract traded during the day. Open interest counts the contracts that are open. It rises by one when a trade opens a position on both sides, stays the same when one side opens and the other closes, and falls by one when both sides close. The Options Clearing Corporation computes it once a day after the market has closed, so the figure on the chain does not move during the day.
Neither number is the same as liquidity. The Options Industry Council calls it a common misconception that they are. How easily an option trades shows in the spread between the bid and the ask and in the number of contracts offered on both sides.
How an option symbol is built
Each listed option has a symbol made of four parts.
| Part | Length | Example |
|---|---|---|
| Root symbol of the underlying, padded with spaces | 6 characters | XYZ |
| Expiration date as year, month, day | 6 digits | 270115 |
| Type, C for a call and P for a put | 1 letter | C |
| Strike price in thousandths of a dollar | 8 digits | 00050000 |
The option symbol XYZ 270115C00050000 is the XYZ call with a strike price of $50 that expires on 15 January 2027. The strike price takes five digits for the dollars and three for the decimals. Brokers and data sites may show the symbol in a form of their own.
Example of reading one row of an option chain
What can go wrong when reading an option chain
The last price can be the oldest number in the row. Options do not trade every minute, and a last price can come from a trade made hours, days or weeks ago, at another price of the stock. The bid and the ask are the current market.
A wide spread makes an option expensive to enter and to leave. A position bought at the ask has lost the spread at once, and an order at the market price in an option with a wide spread can be filled far from the mid price.
A row that looks out of line with its neighbours can be an adjusted option, which delivers something other than 100 shares.
Terms used on this page
- Option chain
- The table of every listed option on one underlying, arranged by expiration date and strike price, with the calls on one side and the puts on the other.
- Bid
- The highest price that buyers are offering for an option at the moment. A seller who wants to trade at once receives the bid.
- Ask
- The lowest price that sellers are asking for an option at the moment. A buyer who wants to trade at once pays the ask.
- Bid-ask spread
- The difference between the ask and the bid. It is a cost of trading, because a position bought at the ask and sold at once at the bid loses the spread.
- Mid price
- The price halfway between the bid and the ask. It is an estimate of what an option is worth, not a price at which an order is sure to be filled.
- Volume
- The number of contracts of an option traded during the current trading day. It starts again from zero every day.
- Open interest
- The number of contracts of an option that are open, which means not yet closed, exercised or expired. The Options Clearing Corporation computes it once a day after the close, so the figure does not move during the trading day.
- Option symbol
- The code that names one listed option. It is made of the root symbol, the expiration date as year, month and day, the letter C or P, and the strike price.
Sources
- Understanding the Bid and Ask Prices for Options, The Options Industry Council (read 29 September 2026). Article of August 2024.
- Open Interest: Why It Matters, The Options Industry Council (read 29 September 2026). Article of October 2025.
- General Information, The Options Industry Council (read 29 September 2026). Frequently asked questions.
- Basics, The Options Industry Council (read 29 September 2026). Frequently asked questions.
- Technical Information, The Options Industry Council (read 29 September 2026). Frequently asked questions.
- Options Symbology Initiative, The Options Clearing Corporation (read 29 September 2026). Version 1.8 of 2008, in the copy kept by the Internet Archive.