Basic net loss per share is determined by dividing net loss by the weighted average shares of common stock outstanding during the period, without consideration of potentially dilutive securities except for those shares that are issuable for little or no cash consideration. Diluted net loss per share is determined by dividing net loss by diluted weighted average shares outstanding. Diluted weighted average shares reflects the dilutive effect, if any, of potentially dilutive common shares, such as stock options and warrants calculated using the treasury stock method. In periods with reported net operating losses, all common stock options and warrants are generally deemed anti-dilutive such that basic net loss per share and diluted net loss per share are equal. However, in certain periods in which the exercise price of the warrants was less than the last reported sales price of Delcath’s common stock on the final trading day of the period and there is a gain recorded pursuant to the change in fair value of the warrant derivative liability, the impact of gains related to the mark-to-market adjustment of the warrants outstanding at the end of the period is reversed and the treasury stock method is used to determine diluted earnings per share.

	June 30,
(in thousands, except share data)	2019			2018
Net (loss) income - basic	$	(13,853	)	$	527
Adjustment for gain on warrant income		—			(619	)
Net loss - diluted	$	(13,853	)	$	(92	)

Weighted average shares outstanding - basic*		72,069,390			788,512
Weighted average shares outstanding - diluted*		72,069,390			799,430

Net loss per share - basic*	$	(0.19	)	$	0.67
Net loss per share - diluted*	$	(0.19	)	$	(0.12	)

^*reflects a one-for-five hundred (1:500) reverse stock split effected on May 2, 2018.

At June 30, 2019, the Company had 53.4 million pre-funded warrants outstanding. The following table provides a reconciliation of the weighted average shares outstanding calculation for the three and six months ended June 30, 2019:

(in thousands)	Three months ended June 30, 2019		Six months ended June 30, 2019
Weighted average shares issued		17,910,886		18,676,912
Weighted average pre-funded warrants		53,392,478		53,392,478
Weighted average shares outstanding		71,303,364		72,069,390

The following potentially dilutive securities were excluded from the computation of earnings per share as of June 30, 2019 and 2018 because their effects would be anti-dilutive:

	June 30,
	2019		2018
Stock options		1,166,667		—
Common stock warrants - equity		4,202,909		—
Common stock warrants - liability		125,029		2,116,296
Assumed conversion of convertible notes		335,697		1,116,255
Total		5,830,302		3,232,551