What is the expected move?
In one line: The expected move is the size of the price swing the options market expects by a given expiry, roughly one standard deviation, read from the price of the at-the-money straddle or from implied volatility.
How it works
The expected move is the market's own guess at how far a stock could travel by a certain date. It's built into option prices. You don't predict it; you read it.
Two quick ways to find it:
- The straddle. Add the price of the at-the-money call and the at-the-money put for the expiry. That total is about what the market expects the stock to move, up or down.
- The formula. Stock price × Implied volatility × the square root of (days ÷ 365).
Both give a one-standard-deviation move. In the model, the stock finishes inside that range about 68% of the time. So it's a range the stock lands in most of the time, not a wall it can't cross. About one time in three, it ends up outside.
Sellers in the wheel strategy use it to see whether their strike sits inside or outside the range the market already expects.
An example (hypothetical)
An illustration, not a trade idea. Made-up stock XYZ trades at $50. Its 30-day implied volatility is 30%.
Formula: $50 × 0.30 × √(30 ÷ 365) ≈ $50 × 0.30 × 0.29 ≈ $4.30.
So the expected move is about $4, giving a range of roughly $46 to $54 by expiry. A $45 put sits just outside the range.
| XYZ at expiry | Inside the range? | Short $45 put sold for $0.80 |
|---|---|---|
| $54 | Yes | +$80 |
| $50 | Yes | +$80 |
| $46 | Yes | +$80 |
| $44 | No, lower | Assigned at $45: +$80 − $100 = −$20 |
| $38 | No, far lower | Assigned at $45: +$80 − $700 = −$620 |
The last two rows are the outside-the-range case. On the downside alone, the model puts that at about one time in six. "Outside the expected move" doesn't mean "won't happen". It means "less likely", and the loss when it does is larger than every premium in the table.
Why it matters for sellers
The expected move tells you how the market is pricing your premium. A strike inside the range pays more and gets assigned more. A strike outside pays less and gets assigned less. There's no strike that is both far away and well paid.
Watch for a trap: the expected move is a big number right before earnings, because implied volatility is high. Selling just outside that range can feel smart. The stock can still gap through it. Earnings moves are exactly the kind the bell curve underestimates.
A good habit: before you sell, write down the expected move and where your strike sits. Then write the loss if the stock lands two expected moves against you. That second line is the trade's real cost.
Questions
How accurate is the expected move?
It's a one-standard-deviation estimate, so the stock lands inside it about two times in three if the model holds. It's often too small around earnings and big news, when real moves are larger than the curve assumes.
Is the expected move the same as the straddle price?
Nearly. The at-the-money straddle price is the simplest reading of it, and some traders scale it down a little. The formula using implied volatility gives a similar answer.
Should I sell options outside the expected move?
It lowers the chance of assignment and the premium with it. It doesn't remove the risk: about one expiry in three lands outside the range, and the loss there can outweigh many small premiums.
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