Supply breakdown
Shares as of Oct 26, 2026| Category | Shares | % | Value | Status |
|---|---|---|---|---|
| Circulating | 147.82M | 100.0% | $31.94B | Estimated |
| Free float | - | - | - | Unavailable |
| Insider-held, unrestricted | - | - | - | Unavailable |
| Locked team funds | - | - | - | Unavailable |
| Other restricted (unlisted classes only) | - | - | - | Unavailable |
| Total outstanding | 147.82M | 100.0% | $31.94B | Verified |
| Ownership views (overlap the categories above, never added) | ||||
| Institutional holdings (13F) | 142.23M | 96.2% | $30.73B | Estimated |
| Insider-held, all (Forms 3, 4, 5) | - | - | - | Unavailable |
Institutional and insider holdings can include both tradable and locked shares, so they are shown for reference and never added to the total. Check: no class has more shares deducted than it has outstanding, and the review found no shares that may be counted twice: reconciles.
Valuation
- Traditional$31.94B
- Fully diluted-
- Circulating$31.94B
- Free float-
- Locked team value$0
- Other restricted value$0
Locked and restricted shares
Not reviewed yet.
Institutional holders
13F, quarter ended Jun 30, 2026| Holder | Shares | % of total |
|---|---|---|
| FMR LLC | 18.22M | 12.32% |
| BlackRock, Inc. | 15.99M | 10.81% |
| PRIMECAP MANAGEMENT CO/CA/ | 15.15M | 10.25% |
| VANGUARD CAPITAL MANAGEMENT LLC | 9.65M | 6.53% |
| STATE STREET CORP | 7.34M | 4.97% |
| VANGUARD PORTFOLIO MANAGEMENT LLC | 6.60M | 4.47% |
| GEODE CAPITAL MANAGEMENT, LLC | 4.45M | 3.01% |
| WELLINGTON MANAGEMENT GROUP LLP | 3.12M | 2.11% |
| NORGES BANK | 2.58M | 1.75% |
| MORGAN STANLEY | 2.41M | 1.63% |
Sum of long share positions in Form 13F reports for the quarter. 13F covers managers with over $100M in US equities; some positions are reported by more than one filer.
Insiders
Forms 3, 4 and 5Form 4 aggregation pending
Share classes
| Class | Listing | Shares outstanding | As of |
|---|---|---|---|
| Common stock | BIIB on Nasdaq | 147,820,223 | Oct 26, 2026 |
Notes and sources
- BIOGEN INC. 10-Q for period ended 2026-09-30, Cover page (0000875045-26-000096)
- SEC public float (non-affiliates): $18.38B as of Jun 30, 2025, from the 10-K cover. It is a dollar value at a past date, not circulating supply.