How to read an options expected move

A fictional stock trades at $200. An options table shows an expected move of ±$14.60 for an expiry four weeks away, with a price range of $185.40 to $214.60. A $180 put sits below that range. How much reassurance should its seller take from the distance?

The expected move estimates the scale of movement priced into options for a particular period. It gives no direction, forecast or guarantee. Before using it to compare strikes, identify the expiry, the calculation method and the time of the underlying quotes. Those details decide what the boundaries mean.

Read across one expiry row

OMP's free, signed-out SPY options page is one place to see these figures. Its expected-move table shows expiry, time left, at-the-money implied volatility, expected move in price units and percentage terms, and a price range. Check the page's “Data as of” timestamp: the figures are a snapshot, so a later quote can produce a different range. Missing figures appear as unavailable.

Read the fields together. “At the money”, or ATM, means a strike at or near the underlying's price. IV is annualised; the expected-move percentage applies to the selected expiry. A 30% IV reading beside a four-week expiry therefore does not mean the stock is expected to move 30% in four weeks.

In the fictional row, $14.60 is 7.3% of $200. The displayed lower and upper prices subtract and add that amount to the reference share price. The calculation says nothing about whether the next move will be up or down.

Find out which calculation produced the move

One common estimate adds the prices of an ATM call and put with the same expiry and strike. Together those options form a straddle, as the Options Industry Council's straddle guide explains. Hypothetical reference premiums of $7.70 and $6.90 total $14.60 per share.

OMP normally uses a usable call-put pair near the money for its table. Two-sided quotes use midpoints, the average of bid and ask. Where a quote side is missing, the calculation can use a qualifying last trade. An asterisk identifies an ATM-IV fallback when a usable pair cannot be priced. The footnote matters: a straddle-price range and an IV-derived range need not match.

Midpoints are reference prices. Buying or selling either leg may cost more than the midpoint suggests, especially in a thin market. The earlier article on how a small quote spread can span a wide IV range explains why displayed precision deserves caution.

The price range around the last stock price also needs separating from a trade's breakevens. The selected strike may differ from that stock price, and actual entry prices and costs matter. The earnings straddle and breakeven guide works through that separate payoff calculation.

Translate annual IV into the selected period

IV is the volatility input inferred from an option price through a pricing model, according to OIC's technical FAQ. The implied-volatility Learn guide explains the pricing input. A common small-move teaching approximation converts it into a price move:

Move ≈ underlying price × annual IV × √(calendar days / 365)

Use IV as a decimal: 30% becomes 0.30. CME's volatility lesson explains the square-root-of-time scaling. Cboe's standard-deviation example also connects annual IV with shorter-period ranges. This approximation holds volatility constant and leaves out drift; it is not an exact description of future prices.

For our fictional $200 stock at 30% IV with 28 calendar days remaining:

$200 × 0.30 × √(28 / 365) = about $16.62

That gives an approximate range of $183.38 to $216.62. These invented inputs illustrate the formula; they are not SPY quotes or a reproduction of the earlier straddle price.

Holding price and IV fixed, seven days gives about $8.31 either way. Four times as much time doubles the move in this approximation. Holding price and 28 days fixed, doubling IV to 60% doubles the move to about $33.24.

A trading-day calculation uses a different clock. OIC's Rule of 16 uses roughly √252 to translate annual volatility into a daily figure. Keep the day count consistent with the convention; do not put calendar days over 252.

Treat “one standard deviation” as a model statement

Under a normal-distribution assumption, about 68% of outcomes fall within one standard deviation of the mean. About 32% fall outside, spread between both tails. OIC's standard-deviation and tail-risk discussion introduces that framework and the need to consider extreme moves.

Option-implied probabilities come from a risk-neutral pricing model and are not measured real-world odds of future moves. In a simple lognormal model, log returns are normally distributed and prices are lognormally distributed, so exact central price bounds can be asymmetric.

The familiar symmetric range around today's price is an approximation. Actual returns can have skew, jumps and heavier tails; future volatility can differ from the input. A central range for the price at expiration also says nothing about whether the stock touches a boundary earlier and returns.

Do not attach the 68% label automatically to a straddle-price range. OMP may show a separate model-dependent central percentile range, presented as a one-standard-deviation comparison, below the table when the required inputs are available. Its fitted pricing distribution is a mixture and need not be a single lognormal model. Its ordinary expected-move column remains the straddle-based figure, subject to the marked IV fallback.

Neither display supplies the probability that a particular trade will make money. That depends on its payoff, premium, costs and exit timing.

Check whether the expiry includes earnings

OIC's vega explanation notes that anticipated news can raise IV and that IV can change without a stock-price move. For a company reporting earnings, compare the release timing with each expiry. An expiry after the announcement includes exposure to its reaction; one that ends before it does not.

The option still covers its whole remaining life. A 28-day expected move cannot be read as a forecast of the next morning's earnings reaction. Nor should a high annualised IV in a short expiry be compared with a longer expiry without considering time. The premium can embed a concentrated event alongside the rest of the term.

After the announcement, changed IV and less time can alter the range. Use a newly timestamped estimate for a new decision rather than carrying the pre-event boundaries forward.

Use the range to compare strikes, then calculate the loss

The $180 put is below both fictional lower boundaries: $185.40 from the straddle reference and $183.38 from the IV approximation. That locates the strike relative to two estimates. It does not establish a safe selling price or a dependable chance of avoiding assignment.

Assume an unchanged, physically delivered American-style equity put with a $180 strike, a 100-share multiplier and an invented $2-per-share entry premium. If the stock finishes at $160 and the put is assigned, the gross result is:

100 × [$2 − ($180 − $160)] = −$1,800

The example excludes fees, tax, interest, dividends, slippage and early assignment. The OIC cash-secured-put guide explains the obligation to buy shares, substantial downside and possible need to fund early assignment. Setting aside cash does not prevent a loss in the acquired shares.

For a strike comparison, write down the contract's expiry and settlement terms, its executable premium and the loss at prices beyond the displayed range. Check liquidity and the cash needed if assigned. Buying an option instead brings its own premium-loss risk; being inside or outside a range does not settle either trade's merits.

Keep the proposed strike beside the range, and keep the dollar loss beside the strike. Reject a position if that loss or funding obligation would be unacceptable when the range is exceeded.

Disclosure: Options Matrix Pro makes options-analysis software. General education, not financial advice. See our disclaimer.