Expected move is a volatility estimate
Expected move translates implied volatility and time to expiration into an approximate one-standard-deviation price range. A common approximation uses underlying price × implied volatility × the square root of days divided by 365.
It describes a statistical range, not a forecast, target, or maximum possible move. Markets can finish inside or outside the range.
A practical use
If a $100 underlying has 30% implied volatility and 30 days to expiration, the one-standard-deviation expected move is roughly $8.60. A trader may compare that range with option strikes, breakevens, or the width of a defined-risk spread.
Use the same expiration date as the position whenever possible. A weekly expected move does not answer the same question as a monthly option strategy.
What it does not capture
Expected move does not determine direction, liquidity, assignment risk, or the effect of an earnings announcement. Implied volatility can change quickly, so the estimate should be refreshed as the market changes.
Treat it as context for planning and position sizing, not a promise about where price will settle.