Vega Explainer
Vega estimates the change in an option’s theoretical value for a one-percentage-point change in implied volatility, with other inputs held constant. Long options generally have positive vega, while written options generally have negative vega.
A quoted vega is normally a per-share sensitivity, so contract multipliers and position size matter. Longer-dated options often carry more vega because volatility has more time to affect the distribution of outcomes, though strike and product features also shape exposure.
Volatility does not move uniformly across all strikes and maturities. Earnings, policy events, market stress, and protection demand can steepen skew or reshape the term structure, causing one leg to react differently from another even when both are labeled long volatility.
Vega is based on a model and a small parallel change assumption. Real option markets can reprice through jumps, changing correlations, illiquidity, and simultaneous price movement. Portfolio managers should test the full volatility surface and event scenarios, not merely add one vega number.
Vega estimates a premium response to a one-point volatility change.
It does not measure price direction.
Longer contracts often have greater volatility sensitivity.
Different parts of the surface can move independently.
Events can alter skew, term structure, and liquidity together.
Test multiple volatility scenarios.
Explore more "Explainers"
Discover additional explainers across politics, science, business, technology, and other fields. Each explainer breaks down a complex idea into clear, everyday language—helping you better understand how major concepts, systems, and debates shape the world around us.