16. NET LOSS PER SHARE

Basic net loss per share is calculated by dividing net loss by the weighted-average number of common shares outstanding during the period, less shares subject to repurchase, and excludes any dilutive effects of stock-based awards and warrants. Diluted net loss per common share is computed giving effect to all potential dilutive common shares, including common stock issuable upon exercise of stock options, and unvested restricted common stock and stock units. As the Company had net losses for the years ended December 31, 2019, 2018 and 2017, all potential common shares were determined to be anti-dilutive. The following table sets forth the computation of net loss per common share (in thousands, except share and per share amounts):


	Year Ended December 31,
	2019		2018		2017
Numerator:
Net loss	$	(94,940)	$	(91,298)	$	(64,339)
Denominator:
Weighted average common shares outstanding - basic and diluted		64,478,066		56,219,919		47,435,331
Net loss per share - basic and diluted	$	(1.47)	$	(1.62)	$	(1.36)

For the years ended December 31, 2019, 2018 and 2017, the total numbers of securities that could potentially dilute net income per share in the future that were not considered in the diluted net loss per share calculations because the effect would have been anti-dilutive were as follows:


	Year Ended December 31,
	2019	2018	2017
Options to purchase common stock	7,128,247	5,378,008	3,977,160
Warrants to purchase common stock	2,172,899	2,172,899	2,172,899
Restricted stock units	—	199,135	323,819
Performance-based restricted stock units	867,506	395,791	148,216
ESPP shares issuable	78,761	63,413	60,524
Total	10,247,413	8,209,246	6,682,618

The number of potential common shares that would have been included in diluted income per share had it not been for the anti-dilutive effect caused by the net loss, computed by converting these securities using the treasury stock method during the years ended December 31, 2019, 2018 and 2017, was approximately 1.1 million, 1.0 million and 1.0 million, respectively.