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).
Hover a call or put cell — every price is one click away from becoming a leg on your order ticket.
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.
- Measures
- Sensitivity to a $1 move in the underlying.
- Convention here
- Signed decimal; the chain displays the magnitude (the value keeps its sign under the hood — a put's delta can be negative). Multiply by 100 for the familiar "30-delta" shorthand.
In the chain, delta is displayed as a magnitude (the underlying value keeps its sign). 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.
Delta here illustrates the market's ITM odds; the live chain reads exact Greeks per strike.
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 reference price the fill engine derives from the bid and ask, snapped to the SPX option tick — $0.05 below $3.00 and $0.10 at or above it for a single leg, and $0.05 for any multi-leg net price. It is the level a resting order waits for, not the price it fills at: a limit order the market comes to fills at its own limit, once this number has reached it and stayed there for three consecutive seconds. An order priced past this number to begin with fills at it instead — at the value it had the moment the order was placed, and with no waiting period at all.
When the spread is an odd number of ticks the exact midpoint lands half a tick off the grid, so it rounds one tick toward the market maker — up when you buy, down when you sell:
The mid is what limit and stop orders are measured against, and what positions are marked at; market orders don't use it — they fill at the natural price (the ask when buying, the bid when selling). A triggered stop prints at this number, and so does an order that crossed the spread rather than resting — at the value it had when that order was placed. The full rules are in Orders & order types.
Near the money: crossing costs a dime, and the two-tick mid ($2.45) is a real, executable price.
A far wing: the mid is closer to a guess, and your fill is worse than it looks.
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
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.
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.
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.