Implied Volatility and Skew: Why Puts Cost More Than Calls

Two options the same distance from the current price, with the same expiry, will almost never cost the same. The put is usually more expensive.

That asymmetry is the market’s assessment of how equities move, and understanding it is most of what separates traders who use options deliberately from traders who buy calls and hope.

What implied volatility is

Nobody sits down and forecasts implied volatility. It is solved backwards.

Take an option’s market price, feed it into a pricing model, and ask what volatility assumption makes the model output that price. That number is the implied volatility: the market’s collective expectation of movement, extracted from what people are willing to pay.

Two consequences follow immediately. IV reflects demand as well as expected movement, so heavy buying of protection pushes IV up whether or not the underlying becomes more volatile. And IV has no direction. It prices the magnitude of expected movement, never the sign.

Skew: the shape of the curve

Plot implied volatility against strike price. In equity markets the line slopes downward from low strikes to high strikes. Downside puts carry higher IV than equidistant upside calls.

There are two reinforcing reasons. First, equities genuinely fall faster than they rise. Advances are gradual; declines are sudden and correlated. The distribution of equity returns has a fatter left tail, and the skew prices that asymmetry correctly. Second, demand is structural and one-sided. Institutions holding long portfolios buy puts as insurance continuously, regardless of view, and there is no equivalent natural buyer of upside calls at comparable size. Persistent demand meeting limited supply keeps put IV elevated.

The related shape, the volatility smile, appears in currencies and some commodities where both tails carry elevated IV. Equity indices show a smirk: elevated on the downside only. The shape tells you what the market fears in that asset.

Term structure

IV also varies across expiries.

In the normal state, called contango, longer-dated options carry higher IV than short-dated ones, because more can happen over more time. When the structure inverts, called backwardation, short-dated IV exceeds long-dated. That happens around a known imminent event such as earnings, a court decision or an election. The near contract prices the event; the far contract does not.

Inversion is informative on its own. It says the market has identified a specific near-term uncertainty and tells you exactly where the premium is concentrated.

IV rank: the number that makes IV usable

A raw IV of 45% means nothing without context. It could be historically calm for a biotech and extreme for a utility.

IV rank places current IV within its own trailing one-year range, 0 to 100.

IV rank	What it usually implies
Above 70	Options expensive against their own history; favours selling premium
30–70	Unremarkable
Below 30	Options cheap against history; favours buying premium

This is the most practical IV metric, because it converts an absolute number into a comparison, which is the only form in which any market number is useful.

Earnings and IV crush

The clearest application, and the one that costs beginners most.

Before a scheduled earnings release, IV on near-dated options rises sharply. The uncertainty is real and it is priced. After the release the uncertainty is gone, and IV collapses within minutes whatever the result.

The consequence catches people out constantly: the company beats, the stock rises 6%, and the call bought the day before is worth less than it cost. The gain in intrinsic value was smaller than the loss from the volatility collapse.

What skew tells you that price does not

Skew is a positioning signal as well as a pricing feature. When put IV rises sharply relative to call IV, institutions are paying up for protection, which is information about how the market is positioned that the index level alone does not show.

Steepening skew during a rally carries the same message as narrowing breadth: the advance is being hedged rather than trusted. Neither times a turn; both tell you how much risk the market is carrying.

The practical takeaways

1. Never compare options on price. Compare on implied volatility, and on IV rank.
2. Check term structure before any dated trade. Inversion means an event is priced in.
3. High IV rank favours selling premium, low favours buying. That is a starting bias rather than a strategy on its own.
4. Assume the expected move is already in the premium. You are betting on a move larger than what is priced, which is a harder bet than direction alone.
5. Skew means spreads are not symmetric. A put spread and a call spread of identical width carry different credit and different risk.

Read how options work for the fundamentals underneath this, and options strategies ranked by risk for which structures suit which volatility environment. Model the payoff of any resulting position with the options profit calculator.