The Strategy Builder is a slot on the Charts desk. Pick a structure and it constructs the legs from the live options chain — real strikes, real premiums — then shows what the position pays, when, and how likely the market thinks each outcome is.

It is the same engine the Options Strategies chapter draws its diagrams with, so a structure cannot mean one thing in the guide and another in the tool. This page is about the tool: the two views, the two sliders, and what the numbers are and are not.

Above the chart sit two tabs. They are not two features — they are the same calculation sampled two ways, which is why they can never disagree with each other.

• Payoff — profit and loss across every share price, on one date.
• Heat — profit and loss across every share price on every date between now and expiry, at once.

The stat strip below both — max profit, max loss, break-even, capital, net credit and the static and annualised return — is the same in either view.

Up to three things are drawn, and they carry different weight.

• The solid line is the position at expiry. It is exact arithmetic — at expiry an option is worth its intrinsic value and nothing else, so this line involves no model, no volatility and no assumption about what the stock does. The corners sit on the strikes.
• The dashed line is the position on the slider's date. It is a Black-Scholes estimate, and it is dashed to say so. It only appears once the date slider is moved back from expiry.
• The shaded hill is where the market prices the stock likely to finish. It is the distribution implied by the premiums themselves. Its height is relative to its own peak and carries no money scale — it says where, never how much.

The vertical line is the current share price; the dotted verticals are break-evens. The axis reads as a percentage of the capital the structure ties up — the same basis the Trade Journal and the entry-signal cards use — and falls back to dollars for a position whose loss is unbounded, because there is then no cash figure to divide by.

Drag DATE to the left and the hard expiry line lifts into a curve. The gap between the two lines is time value, and watching it close is the clearest picture of theta this platform draws.

It is also the honest answer to a question a payoff diagram alone answers wrongly. A cash-secured put shows a break-even at, say, $193 — but that is the break-even at expiry. With five weeks still to run, the price at which the position is flat today sits far higher, because the contract still holds the extrinsic value that has not yet come out. The dashed line crosses zero at that price, and it walks down toward $193 as the days pass.

IV scales every leg's volatility together and redraws the dated line and the heat grid at the new level. The figure beside it is the resulting volatility; reset returns it to what these premiums actually imply.

It answers “what if volatility were half again as high” — which is the question an earnings date inside a contract poses, and one the expiry line cannot answer at all, because at expiry volatility no longer matters. A short option loses on a volatility spike and gains on a crush, before the stock has moved at all.

Rows are share prices, columns are dates from today across to expiry, and each cell is what the position is worth at that price on that date — as a percentage of the capital tied up, or in dollars when there is no capital figure.

The diagonal boundary running through the middle is the break-even walking down and to the right over the life of the trade. For a premium seller that boundary is the position: everything above it is a trade that has already worked, and its slope is how much room decay is buying per week.

Beside the tabs is a figure like “market-implied 70% finish above break-even”. It is solved from the premiums in front of you: the probability the option market is currently pricing for the stock finishing on the profitable side of this structure at expiry.

Two things it is not. It is not a forecast — it is a reading of what the chain costs, and the market is wrong all the time. And it is the risk-neutral probability, the one an option price contains, which differs from the real-world probability by the premium investors charge for bearing risk. It is a description of a condition, not a prediction of an outcome.

It is computed from the same break-evens printed in the stat strip rather than estimated separately, so the percentage and the price it refers to can never drift apart.

The expiry line is arithmetic. Everything dated before it — the dashed line, the heat grid, the shaded range and the percentage — is Black- Scholes, and it assumes:

• European exercise. US equity options can be assigned early, most often around an ex-dividend date on a short call. No payoff tool models this, including this one; it is worth knowing rather than discovering.
• No dividends. A short call on a paying stock is worth slightly less than this prices it.
• One volatility per leg, held flat to expiry. Real volatility moves and is not the same at every strike. The IV slider exists so a different level can be looked at rather than assumed away.
• One expiry. Legs expiring on different dates — a calendar or a diagonal — have no single expiry line, and the builder says so rather than drawing one.

Where a volatility cannot be solved from a leg's premium, the dated line, the heat tab and the percentage all disappear and the expiry line is shown alone. That is deliberate: a curve drawn from a guessed volatility looks exactly as confident as one drawn from a real one.

Everything here describes conditions and reference levels for your own analysis, not instructions to trade. Confirm every price with your broker before acting on it.