Option prices contain a forecast. Not of direction, but of how far the market thinks the underlying might move before expiry. Traders call this the expected move, and it can be estimated in seconds from the option chain.
This article shows two ways to calculate it, works through figures, explains what the range does and does not mean, and covers how traders use it for strike selection, event planning and sizing.
Method 1: from implied volatility
Implied volatility is quoted as an annual percentage. To convert it to a move over a shorter period, multiply by the square root of the fraction of a year remaining.
Formula: one standard deviation move = price × implied volatility × √(days to expiry ÷ 365).
Illustration: index at 24,000, implied volatility of 9 percent, 14 days to expiry. The square root of 14 ÷ 365 is about 0.196. So the one standard deviation move is 24,000 × 0.09 × 0.196, about 423 points.
Under the simplifying assumption of a normal distribution, the market is pricing roughly a two-in-three chance that the index ends within about 423 points of 24,000, that is between about 23,577 and 24,423, by expiry, and roughly a one-in-three chance that it ends outside that range.
Doubling the range to two standard deviations, about 846 points, covers roughly 95 percent of outcomes under the same assumption.
Time scales with the square root. Four times as long does not mean four times the range; it means about twice the range. With the same implied volatility, a move priced at 423 points over 14 days would be roughly 211 points over three and a half days and roughly 846 points over eight weeks.
Method 2: from the at-the-money straddle
A quicker shortcut uses the prices of the at-the-money call option and put option together, known as the straddle.
In the same illustration, the 24,000 call option is about 170 and the 24,000 put option about 160. The straddle costs about 330.
The straddle price is a common quick estimate of the expected move to expiry: about 330 points either side, a range of roughly 23,670 to 24,330.
Notice that this is smaller than the one standard deviation figure of 423. That is expected: mathematically, the at-the-money straddle is worth roughly 0.8 times the one standard deviation move. Some traders use the straddle as is; others divide by 0.8 to approximate one standard deviation. Either way, be consistent.
The straddle method has a practical advantage: it uses actual traded prices, so it automatically reflects skew, upcoming events and anything else the market is pricing.
What the range means, and what it doesn't
It is a market estimate, not a prediction. It reflects the prices people are paying for options today. Realised moves are frequently larger or smaller.
It says nothing about direction. A large expected move means the market is pricing uncertainty, not a rise or fall.
Real returns have fat tails. Large moves happen more often than a normal distribution suggests. The one-in-twenty event outside two standard deviations arrives more often than one in twenty in practice.
It changes constantly. As implied volatility rises or falls and time passes, the range shrinks or widens. Recalculate rather than relying on an old figure.
Options are often priced a little rich. Over long periods, implied volatility has tended on average to exceed the volatility that actually followed, which is why sellers earn a premium on average, and why they occasionally suffer large losses when the realised move far exceeds the estimate.
How traders use it
Strike selection. A seller of a credit spread might place short strikes at or beyond the expected move, so the price must move further than the market expects before the position is threatened. A buyer might ask whether their target lies within or beyond what is priced.
Judging event pricing. Before results or a policy decision, the straddle shows the move priced for the event. If you expect a larger move than priced, buying options may make sense; if smaller, selling might. If you have no edge on the size of the move, neither is attractive.
Comparing with history. How big have past moves been around similar events or periods? If the priced move is far larger than typical realised moves, options may be expensive, and the opposite if far smaller.
Sizing. Estimating the loss if the price moves one or two expected moves against a position is a simple stress test.
Setting realistic targets. A directional view that needs a move three times the priced range in two days needs a strong reason.
A worked event example
Illustrative only. A stock trades at 1,500, with results due tomorrow and options expiring next week. The at-the-money straddle costs 90, so the market is pricing a move of roughly 90, or 6 percent.
Looking back at the last eight results, the stock's move on the day after results averaged about 4 percent, with two moves above 6 percent.
A trader buying the straddle needs a move larger than 90 to profit at expiry, larger than most past reactions. After the results, implied volatility will usually fall sharply, so even a moderate move may leave the straddle worth less than was paid.
A trader selling it would profit on a typical reaction but faces a large loss on a surprise, which has happened twice in eight quarters. A defined-risk structure, such as an iron condor, caps that loss.
Neither trade is obviously right. The expected move turns a vague feeling into a specific question: will the move be bigger or smaller than 90?
An account with implied volatility on the chain
Check straddle prices and implied volatility for any expiry in seconds. Free to open
Figures are illustrations only. This is educational material, not advice, and no position is recommended. We run no tips group and no signal service, we manage nobody's money, and no return is promised. Derivatives can lose more than the amount blocked against them.
Disclosure: the account-opening link on this page is under Atul Shrivastava's Zerodha Authorised Person registration (NSE AP Reg: AP2516003481; Zerodha Broking Ltd. SEBI Reg: INZ000031633) and earns a revenue share. TheFinBaba is not a SEBI-registered Investment Adviser — this content is educational, not investment advice.
Frequently Asked Questions
What is the expected move in options?
The size of move, in either direction, that option prices imply for the underlying by a given expiry. It is an estimate of range, not direction.
How do I calculate the expected move?
Multiply the price by implied volatility and by the square root of days to expiry divided by 365 for one standard deviation, or use the at-the-money straddle price as a quick estimate.
Why is the straddle smaller than the one standard deviation move?
Mathematically, the at-the-money straddle is worth roughly 0.8 times the one standard deviation move, so the two estimates differ by about that factor.
How accurate is the expected move?
It is a market estimate. Actual moves are often larger or smaller, and large moves happen more often than a normal distribution suggests.
How do traders use the expected move?
For placing strikes relative to the priced range, judging whether event moves are expensive or cheap compared with history, stress-testing positions and setting realistic targets.
Related Reading
- Why moves matter most near expiry
- India VIX as a volatility gauge
- Priced versus realised volatility
- Straddles and strangles compared
- Choosing strikes around a range
- Capping the loss on a range trade
Disclaimer: TheFinBaba provides educational content only - this is not investment advice. Trading involves risk of loss.
