Earnings per Share

12 Months Ended

Dec. 31, 2025

Earnings Per Share [Abstract]

Earnings per Share

Note 15: Earnings per Share

Basic and diluted shares outstanding used in our earnings per share calculation are calculated as follows:

	For the Years Ended December 31,
(In millions)	2025		2024		2023
Numerator:
Net income attributable to Biogen Inc.	$	1,292.9	$	1,632.2	$	1,161.1
Denominator:
Weighted-average number of common shares outstanding	146.5		145.6		144.7
Effect of dilutive securities:
Time-vested restricted stock units	0.5		0.3		0.7
Performance stock units settled in stock	0.1		—		0.2
Dilutive potential common shares	0.6		0.3		0.9
Shares used in calculating diluted earnings per share	147.1		145.9		145.6

Amounts excluded from the calculation of net income per diluted share because their effects were anti-dilutive were insignificant.