Earnings Per Share

Basic earnings per share (EPS) is calculated using the weighted average number of common shares outstanding during the period and includes the effect of any participating securities as appropriate. Participating securities consist of unvested restricted stock issued to our employees and non-employee directors that provide dividend rights.

Diluted EPS is calculated assuming the issuance of common shares for all potentially dilutive securities, provided the effect is not antidilutive. For all periods presented, our contingent convertible senior notes did not have a dilutive effect and, therefore, were excluded from the calculation of diluted EPS. See Note 3 for further discussion of our convertible senior notes and contingent convertible senior notes.

A reconciliation of basic EPS and diluted EPS is as follows:



	Three Months Ended June 30,					Six Months Ended June 30,
	2018			2017		2018		2017
	(in millions, except per share data)
Net income (loss) available to common stockholders	$	(40	)	$	470	$	228	$	547
Effect of dilutive securities	—			59		—		72
Diluted income (loss) available to common stockholders	$	(40	)	$	529	$	228	$	619

Weighted average common and common equivalent shares outstanding - basic	909			908		908		907
Effect of dilutive securities	—			206		—		146
Weighted average common and common equivalent shares outstanding - diluted	909			1,114		908		1,053

Net income per share attributable to Chesapeake:
Basic	$	(0.04	)	$	0.52	$	0.25	$	0.60
Diluted	$	(0.04	)	$	0.47	$	0.25	$	0.59

Shares of common stock for the following securities were excluded from the calculation of diluted EPS as the effect was antidilutive:
Common stock equivalent of our preferred stock outstanding	60			—		60		60
Common stock equivalent of our convertible senior notes outstanding	146			—		146		—
Common stock equivalent of our preferred stock outstanding prior to exchange	—			—		—		1
Participating securities	1			1		1		1