What Is Volatility
Understand the two types of volatility, why they matter, and how options traders use volatility as their primary edge.
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The Most Misunderstood Concept in Trading
Most traders think options are about direction — will the stock go up or down? Professional options traders know better. Options are about volatility — how much will the stock move, regardless of direction?
If you understand volatility, you can profit when stocks go up, down, or sideways. If you do not understand volatility, you will buy overpriced options and sell underpriced ones without knowing it. Volatility is the edge.
Two Types of Volatility
Historical Volatility (HV)
Historical volatility measures how much a stock has actually moved in the past. It is calculated from real price data — typically the standard deviation of daily returns over 20 or 30 trading days, annualized.
Example: If AAPL has a 20-day HV of 25%, that means AAPL has been moving at a pace consistent with a 25% annual range. In daily terms, that is roughly 1.6% per day (25% divided by the square root of 252 trading days).
HV tells you what the stock has done. It is backward-looking.
Implied Volatility (IV)
Implied volatility is what the options market expects the stock to do in the future. It is derived from current option prices using an options pricing model (Black-Scholes or similar).
Example: If AAPL options are priced with an IV of 30%, the market expects AAPL to move at a pace consistent with 30% annually over the life of the option.
IV tells you what the market thinks will happen. It is forward-looking.
Why the Gap Between HV and IV Matters
Here is where the money is made. When IV is significantly higher than HV, options are overpriced. The market is expecting more movement than the stock has been delivering. This is your signal to sell premium — sell options, collect that inflated price, and profit as IV contracts.
When IV is significantly lower than HV, options are underpriced. The market is expecting calm while the stock has been moving aggressively. This is rarer, but when it happens, it is a signal to buy premium.
The structural reality: IV is almost always higher than HV. This is because option buyers are willing to pay a premium for insurance (puts) and leverage (calls). Studies consistently show that implied volatility overstates actual realized volatility by 2-4 percentage points on average across the S&P 500.
This overstatement is the volatility risk premium — and it is the single biggest reason why selling options is profitable over time.
How to Read Volatility Numbers
When you see an IV of 30%, here is what it means in practical terms:
Annual expected move: The stock is expected to move within plus or minus 30% over the next year, approximately 68% of the time (one standard deviation).
Monthly expected move: Divide annual IV by the square root of 12. So 30% / 3.46 = 8.7% per month.
Weekly expected move: Divide annual IV by the square root of 52. So 30% / 7.21 = 4.2% per week.
Daily expected move: Divide annual IV by the square root of 252. So 30% / 15.87 = 1.9% per day.
If AAPL trades at $175 with 30% IV, the market expects a daily range of roughly $3.30 (1.9% of $175). In a month, the expected range is about $15.20 (8.7% of $175).
Volatility Is Not Direction
A stock can have high volatility and go up. A stock can have high volatility and go down. A stock can have low volatility and barely move in either direction.
When you sell a straddle because IV is high, you are not betting the stock will stay perfectly flat. You are betting that the stock will move less than the market expects. If IV implies a $15 monthly move and the stock moves $10, you win — even if it moved $10 in one direction.
This distinction is everything. Volatility trading frees you from the guessing game of predicting direction. You are trading the magnitude of movement, and the data shows the market consistently overestimates that magnitude.
Volatility Expands and Contracts
Volatility is mean-reverting. It does not stay high forever, and it does not stay low forever. When IV spikes during a market panic, it eventually comes back down. When IV compresses during a calm market, it eventually spikes again.
This mean-reversion is predictable and tradeable. The entire volatility trading framework we will build in this course is based on this principle: sell when IV is high, buy when IV is low, and let mean-reversion work in your favor.
That starts with knowing exactly when IV is "high" or "low" — which is what IV Rank tells you. That is our next lesson.