Net Loss Per Share

12 Months Ended

Dec. 31, 2019

Basic earnings per share is calculated by dividing net income (loss) attributable to common stockholders by the weighted average number of shares of common stock outstanding, net of the weighted average unvested restricted stock subject to repurchase by the Company, if any, during the period. Diluted earnings per share is calculated by dividing the net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding, adjusted for the effects of potentially dilutive common stock, which are comprised of stock options, restricted stock units and stock warrants, using the treasury-stock method, and convertible preferred stock, using the if-converted method. Because the Company reported losses attributable to common stockholders for all periods presented, all potentially dilutive common stock is antidilutive for those periods.

The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders during the years ended December 31, 2019, 2018, and 2017 (in thousands, except per share data):



	Year Ended December 31,
	2019			2018			2017
Net loss	$	(54,890	)	$	(28,321	)	$	(32,849	)
Weighted-average common shares outstanding	105,805			102,149			94,865
Net loss per share — basic and diluted	$	(0.52	)	$	(0.28	)	$	(0.35	)

The following table presents the number of anti-dilutive shares excluded from the calculation of diluted net loss per share attributable to common stockholders at December 31, 2019, 2018, and 2017 (in thousands):



	December 31,
	2019	2018	2017
Options to purchase common stock	10,626	14,115	16,714
Common stock warrants	1,459	1,459	1,459
Unvested restricted stock units	5,891	5,376	4,284
Total shares excluded from net loss per share attributable to common stockholders	17,976	20,950	22,457