Stock Volatility and Risk for Beginners
For example here one can find the volatilities of stocks and indices:
http://www.optionstrategist.com/calculators/free-volatility-data
One can also compute it yourself if one collects the daily closing stock prices
in a database or Excel table.
Below, the column "hv100" means the historical volatility over the last 100 days.
IBM is of course the computer giant company.
SPY is the S&P500 index, ie the average index over 500 companies listed in the S&P list.
Code:
Symbol (option symbols) hv20 hv50 hv100 DATE curiv Days/Percentile Close
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IBM 32 27 25 160219 21.85 600/ 87%ile 133.08
SPY 22 21 18 160219 16.77 600/ 88%ile 192.00
Interpretation:
Investing in IBM has a 25% risk over a period of 100 days, ie. one can expect that after 100 days
the stock price will be most probably between +25% and -25% around the current mean price as of today ($133.08), that is between $99.81 and $166.35.
And the following is the formula for computing the daily volatility (using year = 252 trading days):
DailyVola% = AnnualVola% * sqrt(1 / 252)
If we assume that the annual volatility of IBM is 25% then:
DailyVola% = 25 * sqrt(1 / 252) = 1.57%
With that formula one can also compute the weekly vola:
WeeklyVola% = 25 * sqrt(5 / 252) = 3.52%
And of course also the monthly vola:
MonthlyVola% = 25 * sqrt(21 / 252) = 7.22%
As said: volatility means the deviation in percent around the mean price, ie. up or down.
As said: vola% can also be interpreted as the risk% of the investment.