IV vs HV explained

Two volatility numbers appear constantly in options analysis: implied volatility (IV) and historical volatility (HV). They measure different things, move independently of each other, and tell you different stories about a stock. Comparing them is one of the most powerful and underused tools in options trading.

What each one measures

Implied volatility (IV) is forward-looking. It's derived from current option prices and reflects what the market expects a stock's volatility to be over the next 30 days (typically). IV is the market's collective forecast, the price of uncertainty.

Historical volatility (HV) is backward-looking. It measures how much a stock has actually moved over a specific past period, typically 10, 20, 30, or 90 days. HV is calculated from actual daily price returns and annualized. It tells you what the stock did, not what the market expects.

The key relationship

In a perfectly efficient market, IV would equal expected future realized volatility, and HV (as a proxy for recent realized volatility) would be similar to IV. In practice, they diverge, and that divergence reveals opportunity.

The persistent reality: IV systematically overstates actual realized volatility over time. This means the market consistently prices in more movement than actually occurs. Options sellers harvest this difference, they're collecting premium that's slightly inflated relative to the actual risk.

Reading the IV vs HV relationship

IV significantly higher than HV: Options are expensive relative to recent actual movement. The market is pricing in significantly more volatility than the stock has been delivering.

This is the classic setup for premium sellers. Selling iron condors, covered calls, or cash-secured puts when IV is running hot relative to HV gives you a structural edge, you're collecting inflated premium on uncertainty that may not materialize.

IV significantly lower than HV: Options are cheap relative to recent actual movement. The stock has been moving more than the market is pricing in, unusual, often temporary.

This can be a signal for options buyers. When IV is running well below recent realized moves, buying options may offer favorable risk/reward.

IV approximately equal to HV: No significant edge in either direction from the volatility relationship alone. Other factors (IV rank, upcoming catalysts, skew) should drive your strategy decision.

Practical examples

Example 1, Premium selling edge: AAPL 30-day HV: 18% AAPL current IV: 34% IV/HV ratio: 1.89

IV is nearly double recent realized volatility. Options are significantly overpriced relative to how the stock has actually been moving. Premium sellers have a clear statistical edge.

Example 2, Buying opportunity: TSLA 30-day HV: 55% TSLA current IV: 38% IV/HV ratio: 0.69

TSLA has been moving more than options are implying. Options look cheap. This is the type of environment where buying straddles or directional options may offer better-than-normal value.

IV vs HV for timing entries

Beyond identifying whether options are cheap or expensive, the IV/HV comparison helps time entries:

• When IV is rising rapidly toward HV or above: A volatility spike may be underway. Sellers should wait for IV to peak before entering; buyers should enter early.
• When IV is falling toward HV: Mean reversion in volatility is occurring. Good time for sellers to collect elevated premium that may normalize.
• When IV has been stable and near HV for an extended period: Options are fairly priced. Look to other factors, trend, catalyst, IV rank, for your edge.

The IV/HV ratio and earnings

The IV vs HV dynamic is most extreme around earnings announcements. In the week before a major earnings release, IV can spike to 2–4× the recent HV as market participants price in binary event risk.

This IV spike above HV is precisely the opportunity earnings premium sellers are targeting. They collect the inflated IV and wait for post-earnings IV crush to bring IV back in line with (or below) HV.

Which HV lookback to use?

HV can be calculated over different lookback periods, 10-day, 20-day, 30-day, 90-day. Each tells a slightly different story:

• 10-day HV: Very recent, most sensitive to short-term movement. More volatile itself.
• 20–30-day HV: Most commonly compared to IV (both cover roughly one month). Most useful benchmark.
• 90-day HV: Longer-term context. Smooths out short-term spikes.

For most IV vs HV comparisons, use 30-day HV alongside 30-day IV for an apples-to-apples comparison.

Related terms: Implied volatility, IV rank, IV percentile, historical volatility, Vega, IV crush

Try it on Stryke: Monitor live IV and compare against historical volatility in the Options Screener.