What Is Vega? Implied Volatility Sensitivity Explained

Vega measures how much an option’s price changes when implied volatility moves by 1 percentage point. It’s one of the Greeks, and it’s the one that quietly decides whether your options trade is a winner or a loser — even when you got the direction right.

The basic definition

If an option has a vega of 0.15, a 1-point increase in implied volatility will add about $0.15 to its price. A 1-point decrease will subtract about $0.15. That’s it — vega tells you how sensitive the option is to changes in IV.

Vega is positive for both calls and puts when you’re long. Higher volatility means bigger expected price swings, which means more optionality, which means higher premiums. Lower volatility means smaller expected swings and lower premiums.

What is implied volatility?

Implied volatility (IV) is the market’s forecast of how much the underlying will move between now and expiration. It’s expressed as an annualized percentage. An IV of 20% means the market expects the stock to move within a ±20% range over the next year (in statistical terms, one standard deviation).

IV is forward-looking. It’s not a measurement of past movement — it’s the market’s collective opinion about future movement, derived from the current prices of options. When traders expect big moves, IV goes up. When things calm down, IV drops.

Why vega matters

You can be dead right about direction and still lose money on an options trade if volatility moves against you. Here’s a concrete example.

Say you buy a call option before a big earnings report. The stock is trading at $100, your strike is $105, and IV is elevated to 60% because everyone expects fireworks. You pay $3.00 for the option.

Earnings come out. The stock moves up to $104 — a decent move, in your favor. But IV immediately collapses from 60% to 30% now that the event is over. Even though the underlying moved the right direction, vega just sucked a huge chunk of value out of your option. It’s now worth $2.20 instead of the $3.50 you expected.

That’s vega risk. You were right about direction and still lost money, because the volatility you paid for evaporated.

IV crush explained

“IV crush” is the term traders use for sudden, dramatic drops in implied volatility. It happens most reliably around known events:

• Earnings announcements — IV often drops 30-50% right after the report
• FOMC decisions — IV compresses as the uncertainty resolves
• Drug trial results — Binary outcomes for biotech can cause massive IV shifts
• Major product launches — Apple events, for instance

The pattern is the same: leading up to the event, IV gets bid up because everyone expects a big move. Once the event resolves and the uncertainty is gone, there’s no reason to price in extra volatility anymore, and IV collapses.

This is why buying options right before earnings is a notoriously bad trade unless you’re getting a huge move. The IV crush alone can eat your gains.

Vega and expiration

Vega is highest for at-the-money options with plenty of time remaining. That makes intuitive sense — when there’s lots of time and the strike is near price, a change in expected volatility has the biggest impact on how much the option could be worth by expiration.

As expiration approaches, vega shrinks. A 0DTE option has very little vega because there’s almost no time left for volatility to matter. That’s why 0DTE traders obsess over gamma (the direction and speed of moves) rather than vega — for an option expiring in hours, what IV is doing barely matters.

For longer-dated positions, vega is a major part of the equation. LEAPS (long-term options) can gain or lose significant value just from IV shifts, even if the underlying does nothing. If you trade longer-dated options, you’re really trading volatility as much as direction.

The practical lesson: know where IV is when you enter a trade. If IV is historically high, you’re buying expensive premium and vulnerable to IV crush. If IV is low, you’re paying less for the same optionality, and an IV expansion can add value even if direction doesn’t cooperate immediately. Vega is the Greek most people ignore until it costs them money.