IV Rank & IV Percentile

IV Rank and IV Percentile are two metrics that contextualize a stock's current implied volatility by comparing it to its own history. IV Rank tells you where current IV sits relative to its 52-week high and low. IV Percentile tells you what percentage of days over the past year had lower IV than today. Both answer the same question: is current IV high or low for this stock?

Why It Matters

A stock's absolute IV number is nearly meaningless without context. An IV of 35% is extremely high for a utility stock that normally trades at 15% IV. That same 35% would be low for a biotech that routinely trades at 60% IV. IV Rank and IV Percentile provide the context that raw IV numbers lack.

These metrics are the primary screening tool for premium sellers. Selling options when IV Rank is above 50% (meaning IV is in the upper half of its range) is a core principle of probability-based trading. Conversely, buying options when IV Rank is low gives you cheaper exposure to potential moves.

How It Works

IV Rank formula:

IV Rank = (Current IV - 52-week Low IV) / (52-week High IV - 52-week Low IV) x 100

IV Rank of 0% means IV is at its 52-week low. IV Rank of 100% means IV is at its 52-week high. IV Rank of 50% means IV is exactly halfway between its high and low.

IV Percentile formula:

IV Percentile = (Number of days in past year with IV below current IV) / (Total trading days in past year) x 100

IV Percentile of 80% means that on 80% of trading days in the past year, IV was lower than it is today. This means current IV is in the top 20% of readings.

Which one should you use?

Both are useful, but they can diverge significantly. Here's why:

• IV Rank is sensitive to outliers. If a stock's IV spiked to 120% for one day during a crash, that extreme sets the high for the entire year. Now, an IV of 50% might show an IV Rank of only 30%, even though IV is elevated for 90% of the year.
• IV Percentile is more robust because it counts days, not extremes. It tells you how often IV has been lower — a more practical measure for most traders.

General guidelines:

• IV Rank or Percentile above 50%: Consider selling premium
• IV Rank or Percentile below 30%: Consider buying premium or avoiding selling strategies
• IV Rank or Percentile above 80%: Strong environment for credit strategies

Quick Example

Stock BCD has the following IV history over the past year:

• 52-week IV low: 20%
• 52-week IV high: 80%
• Current IV: 35%

IV Rank = (35 - 20) / (80 - 20) x 100 = 25%

That looks low — IV is only 25% of the way between its low and high. But the 80% peak was a one-day spike during a market crash. On 85% of trading days, IV was below 35%. So IV Percentile is 85% — current IV is actually elevated by historical standards.

In this case, IV Percentile gives you a more accurate picture.