Option chain & Greeks

The option chain lists every available strike for the session with its calls and puts. It's where you read the market and click to build orders.

Reading the chain

Each row is a strike; calls sit on one side, puts on the other. For each option you'll see:

• Bid — the best price a buyer is offering (what you'd receive selling).
• Ask — the best price a seller is asking (what you'd pay buying).
• Delta (below).

The strike nearest the current SPX price is the at-the-money strike and is highlighted. Strikes are listed on a fixed grid (every 5 points for SPX).

Delta

Delta measures how an option's price responds to a $1 move in the underlying. Every option in the chain — and every open position — carries a live delta that recomputes whenever the clock moves.

Greek	Measures	Convention used here
Delta	Sensitivity to a $1 move in the underlying	Decimal 0..1, unsigned in the chain. Multiply by 100 for the familiar "30-delta" shorthand.

In the chain, delta is shown unsigned. On a position, delta takes a sign from your direction: long calls have positive delta, short calls negative (and the reverse for puts). See Positions & P&L.

Delta is also the chain's built-in probability gauge: a 0DTE option's delta roughly approximates the market-implied odds it expires in the money. That's why strike selection in the strategy builder is usually expressed in delta — "sell the 16-delta put" means "sell the put the market gives ~16% odds of finishing ITM", wherever that strike happens to sit today.

Imputed quotes

When a real bid/ask isn't available for an exact moment, the simulator synthesizes a quote so the chain stays continuous across every second of the session even when the live market was momentarily thin.

Mid-price rules

The mid-price is the midpoint of bid and ask, rounded to the instrument's tick:

• SPX options round to the nearest nickel ($0.05).
• Other options round to the nearest penny ($0.01).

Edge case: when the bid-ask spread is exactly one tick wide, the simulator uses the ask for buys and the bid for sells. The mid is the reference price for limit and stop executions and for marking positions; market orders don't use it — they fill at the natural price (the ask when buying, the bid when selling). The full rules are in Orders & order types.

Building orders from the chain

Click any call or put cell to add it as a leg on your order ticket. Add several legs to build a spread, an iron condor, or any multi-leg structure; they'll execute together as a single atomic order. The ticket previews the net price, fees, and buying-power impact before you submit.

Tips

• Watch the spread, not just the price. The bid-ask gap is the chain's honest liquidity signal: a $0.05-wide quote near the money costs you almost nothing to cross, while a $1.00-wide quote on a far wing means the mid is closer to a guess — and your fill worse than it looks.
• Delta ≈ odds. Scanning the delta column top to bottom gives you the market's live probability map of where SPX might close. The 50-delta strike is the coin flip; the 5-delta wings are the "surely not" zone that occasionally isn't.
• Click legs in the order you think about them. For a spread, click the leg you're selling first, then the protection — the ticket shows the running net credit/debit as you add legs, so you can see the structure's price take shape.