Exhibit No. 11

ARMSTRONG WORLD INDUSTRIES, INC. AND SUBSIDIARIES

COMPUTATION OF EARNINGS PER SHARE
(AMOUNTS IN MILLIONS EXCEPT FOR PER-SHARE DATA)

	Year Ended December 31,
	2010		2009			2008
Basic earnings per share
Net earnings	$	11.0	$	77.7		$	81.0
Net earnings allocated to non-vested share awards		—		(0.4	)		(0.6	)
Net earnings attributable to common shares	$	11.0	$	77.3		$	80.4
Basic weighted average number of common shares outstanding		57.7		56.8			56.4
Basic earnings per share	$	0.19	$	1.36		$	1.42
Diluted earnings per share
Net earnings	$	11.0	$	77.7		$	81.0
Net earnings allocated to non-vested share awards		—		(0.4	)		(0.6	)
Net earnings attributable to common shares	$	11.0	$	77.3		$	80.4
Basic weighted average number of common shares outstanding		57.7		56.8			56.4
Weighted average number of common shares issuable under stock option or unvested stock grants		0.5		0.2			—
Diluted weighted average number of common shares outstanding		58.2		57.0			56.4
Diluted earnings per share	$	0.19	$	1.36		$	1.42