1
Bid and ask
The bid is the displayed buying price and the ask is the displayed selling price; the difference is the spread.
Lesson · Options Trading
Option Chain and Liquidity
Read a synthetic option chain, compare bid and ask prices, quantify spread friction, inspect volume and open interest, and use limit prices deliberately.
Synthetic educational examples
Core concepts
The quote is a bid and an ask; what you pay is the distance between them.
2
Volume and open interest
Volume measures contracts traded during the session; open interest measures outstanding contracts after clearing updates.
3
Execution quality
A directional idea can still produce a poor trade when the spread is wide or the contract is difficult to exit.
Worked example
The default row: the 100 call at 30 DTE with the stock at $100, read the way the drill will ask you to read any row.
1
Bid $3.31, ask $3.46: a spread of $0.15 per share, $15 per contract.As a share of the mid, 0.15 / 3.385 = 4.4%. The percentage is what makes one strike comparable with another.
2
A market buy pays the ask: $346. A market sell later, quote unchanged, receives the bid: $331.The round trip at the market costs the whole spread, $15, before the option has moved at all. Pay it on the way in and again on the way out.
3
A limit at the mid, $3.38, pays $338 if it fills.That saves $8 against the ask on the way in. The cost is that it may not fill, and a limit that never fills is a trade that never happened.
4
Volume 1,121 and open interest 5,801 say the strike is active.They do not change the $0.15. Activity is context for whether you can get out later; the spread is the price of getting in and out now.
Interactive lesson
Pick a row and an expiration, read the spread in dollars and in percent, and set a limit inside the market.
| Strike | Bid | Ask | Mid | Spread % | Volume | Open interest | Delta | IV |
|---|
Synthetic values demonstrate selection mechanics. Volume and open interest do not guarantee a fill or future liquidity. The Delta and IV columns are context only here: Implied Volatility explains IV and Delta and Gamma explains delta.
Select from an option chain
Contract selection starts with the trade thesis and ends with execution quality.
1
Choose expiration
The contract must give the thesis enough time while respecting premium and event exposure.
2
Choose strike
Use Moneyness to match the intended exposure and cost; the sensitivities in Delta and Gamma and Theta and Vega refine the choice.
3
Inspect the market
Compare bid, ask, spread percentage, displayed activity, and open interest.
4
Use a deliberate order
Set a limit based on the displayed market and accept that it may not execute.
Option chain decisions
Score 0 / 0Choose the best answer.
Lesson rule
Change the inputs, calculate the result, and explain the risk before selecting a contract.
Common mistakes
1
Buying the cheapest premiumLow price can reflect low delta, little time, or poor liquidity rather than good value.
2
Using only open interestCurrent spread and depth matter at entry and exit; open interest alone is not enough.
3
Sending market orders into wide spreadsImmediate execution can produce a materially worse price than expected.
Completion standard
✓
Finish when you can read a chain row into a spread in dollars and in percent of the mid, state what a market order pays on the way in and out, and place a limit inside the displayed market.
Activity columns are context; the drill asks you to price the spread and to say what a limit at the mid saves and what it risks.
Model scope: Theoretical values use a simplified European Black–Scholes model with a fixed 4.5% annual rate and no dividend input, so a number here can be reproduced in any calculator that takes those inputs. Listed products, early exercise, dividends, spreads, fees, and market conditions can produce different prices and outcomes.