As discussed in the "Expected Move" post, the expected movement of a stock can be calculated with the following formula, where S subscript 0 is the stock's current price, IV is implied volatility, and the final term is the square root of days to expiration divided by 365:
Though an intimidating formula at first glance, it provides traders with the approximate range in which a stock's price may travel in a given amount of time or days to expiration (DTE). Note: The image above should say plus or minus preceding the square root sign.
To visualize, let's look at an example. Assume a SPY stock's price on low for the year on Feb 11th 2016 as $182.86, with an implied volatility of 28.14%. To calculate the expected move in 30 days, we substitute "DTE" with actual number of dates and solve for EM.
The plus or minus range for each expiration will approximately equate to the EM calculations using the mid-price fills of EM spreads and the MMM value.
Eighteen-year old trader, future connoisseur of options.
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