How to Read Bid & Ask on the Option Chain: Check the Spread% First, Then the Bid and Ask
Every row on the option chain has two prices: the bid and the ask. The bid is the highest price someone is willing to pay right now; the ask is the lowest price someone is willing to sell at. You buy at the ask and sell at the bid — the mid price is only the average of the two, not a fill price. Check the spread% column before you open: a wide spread means a high cost to trade.
What the bid, the ask, and the mid price each mean
Bid: the highest price someone in the market is willing to pay right now. If you want to sell, you fill at the bid.
Ask: the lowest price someone in the market is willing to sell at right now. If you want to buy, you fill at the ask.
Mid price: (bid + ask) ÷ 2, a reference value only. The simulator values open positions at the mid price, but every fill happens at the bid or the ask.
An example: bid $1.80, ask $2.20, so the mid price is $2.00. Buying 1 contract costs $220 ($2.20 × 100), not $200.
Spread%: check this column before you open
Spread% = (ask − bid) ÷ mid price: in the example above: ($2.20 − $1.80) ÷ $2.00 = 20%.
The smaller the spread%, the better: the tighter the bid and ask sit together, the less extra cost you pay to trade.
The chain highlights anything over 20% in red: in the simulator's option chain, cells with a spread% over 20% turn red; when you see red, do not rush in — pick another strike or wait.
When spreads are wide: deep out-of-the-money strikes, near the close, and when the market is jumping around. Example: bid $1.00, ask $1.60, mid $1.30 — the spread% is 46.2%, shown in red.
Which price each side of the trade fills at
Buying to open fills at the ask; selling to open (selling an option) fills at the bid; closing is the reverse: a long position sells at the bid, a short position buys back at the ask.
Closing right away costs you the whole spread: buy 1 contract at $2.20, sell it immediately at $1.80, and you lose $40 on the premium; plus $1.30 in round-trip fees, the total loss is $41.30.
A market order fills at the best bid or ask available at the time; a limit order can wait near the mid price, but if the price never gets there, it never fills.
The order ticket's estimate is priced off the fill price directly: buying shows the ask, selling shows the bid, with the premium and the fee listed; only the floating P&L of open positions is valued at the mid price.
How to practice in the simulator
Check the spread% column before every order: skip rows highlighted red over 20% and practice on strikes with a small spread% first.
Look at the bid and ask before the mid price: the bid and ask decide the fill price; the mid price is only a valuation reference.
Start with 1 long single-leg contract: practice the simplest case first — buy 1 contract and check whether the fill price is the ask and the closing price is the bid.
Review against the trade log: check how far each actual fill was from the mid price, and how much the spread and the fees took in total.
This simulator uses real CBOE option chains delayed about 15 minutes, starts with $10,000 in virtual funds, charges $0.65 per contract per side in fees, and shows P&L net of fees; short-sale margin is a simplified simulated rule at 20% of the strike, not a real broker margin. The simulator is for practicing orders, discipline, and review. It is not investment advice and promises no returns.