Options profit calculator

The calculator is built around the prices you already see. Nothing is fetched — no quotes, no option chains — so the numbers are only as current as what you type, and everything stays in your browser.

The chart plots your profit or loss in dollars (up the side) against the stock price (across). The solid line is P/L at expiration: green where the position makes money, red where it loses. It bends only at the strikes, because at expiration each option is worth exactly its intrinsic value.

The blue line is P/L today — what the position would be worth if the stock jumped to that price right now, valued with Black-Scholes at each leg's implied volatility (read from the price you typed, or the IV field for an estimated leg). The dashed purple line shows the same thing halfway to expiration. The gap between today's line and the expiration line is the time value still in the position; as the days pass it decays and the curve sinks (or rises, for a short-premium trade) toward the expiration line.

The vertical line marks the current stock price and the dots on the zero line are the breakevens. Hover over the chart, or drag a finger across it on a phone, to read every line's P/L at any price.

The table below the chart gives the same answer as a grid: each row is a stock price, each column a date between today and expiration, and each cell the position's P/L if the stock is at that price on that date. The deeper the green or red, the larger the gain or loss.

Max profit and max loss are measured at expiration across every possible stock price, from zero upward. A value is unlimited when the payoff keeps rising or falling as the stock climbs: more calls (or shares) sold than bought means unlimited risk, as with a naked short call; more bought than sold means unlimited upside, as with a long call. On the downside everything is bounded, because a stock can't fall below zero.

Implied volatility (IV) is the market's price for uncertainty, and it drives every theoretical premium. With the stock at $100, 30 days to expiration and a 4.5% rate, the 100-strike call is worth about $3.61 at 30% IV but about $5.32 at 45% IV. Higher IV makes long options more expensive — their breakevens move further away — and pays sellers more for the same strikes.

On the chart, more IV means more time value: today's line sits further from the expiration line and its curve is smoother. As IV falls toward zero, today's line closes in on the expiration payoff. IV also sets the expected move used for the chart's range and for the probability of profit: at 30% IV a $100 stock's one-standard-deviation move over 30 days is about ±$8.60.

IV changes after you open a trade. A position with positive vega gains when IV rises and loses when it falls — the classic example is a long straddle bought before earnings that loses money even though the stock moved, because IV dropped once the news was out. Override the IV to see how a different level would reprice the legs you haven't priced, and the odds.

Probability of profit (POP) is the chance that the position shows any profit at expiration. The calculator models the stock price at expiration as lognormal, with the position's implied volatility (the vega-weighted average of your legs' IVs, or the IV you enter) and a drift of the risk-free rate minus the dividend yield, then adds up the probability of every price range where the expiration P/L is above zero. For the 100/110 bull call spread on a $100 stock at 30% IV with 30 days left, priced at theoretical values ($3.61 and $0.66, a $2.95 debit), that comes to about 37%.