BIIB implied volatility
From the closing options book · October 20, 2026 · updated after every close
BIIB's at-the-money implied volatility was 44.8% at the October 20, 2026 close. Over the past 78 sessions it ranged from 30.0% to 55.8%, putting today's level at an IV rank of 58 and IV percentile of 82.
BIIB at-the-money IV, last 60 sessions
Options were pricing more movement than BIIB actually delivered over the last 20 sessions (44.8% implied against 24.4% realized).
IV rank places today's IV between the period's low (0) and high (100); IV percentile is the share of sessions with lower IV. Both use BIIB's own closing history.
These are the October 20, 2026 closing numbers. Members see BIIB's map move live all session.
Common questions
44.8% at the money at the October 20, 2026 close.
58 over the past 78 sessions (IV percentile 82).
Its IV percentile is 82: high against its own past year.
Compare: implied volatility on other tickers
Measured from the closing options book and rebuilt after every close. Nothing on this page is live. Levels are where dealer hedging is concentrated, not targets or forecasts. Not investment advice.