Net Loss Per Share

The Company computes net loss per share using the two-class method required for multiple classes of common stock and participating securities. The rights, including the liquidation and dividend rights, of the Class A common stock and Class B common stock are substantially identical, other than voting rights. Accordingly, the Class A common stock and Class B common stock share equally in the Company’s net losses. Before the IPO, the Company’s outstanding securities also included convertible preferred stock. The holders of convertible preferred stock did not have a contractual obligation to share in the Company’s losses, and as a result, net losses were not allocated to these securities.

The following table sets forth the calculation of basic and diluted net loss per share attributable to common stockholders during the periods presented. The shares issued in the IPO and the private placement and the shares of Class A and Class B common stock issued upon conversion of the outstanding shares of convertible preferred stock in the IPO are included in the table below weighted for the period outstanding in the year ended December 31, 2018. Additionally, the voluntary conversions of Class B common stock into Class A common stock are included in the table below weighted for the period outstanding in the year ended December 31, 2018:



	Year ended December 31,
	2018						2017						2016
	Class A			Class B			Class A			Class B			Class A			Class B
Numerator:
Net loss attributable to common stockholders	$	(138.7	)	$	(346.2	)	$	(3.6	)	$	(108.1	)	$	(6.1	)	$	(204.1	)
Denominator:
Weighted-average number of common shares outstanding used in computing basic and diluted net loss per common share	102.6			256.0			6.3			189.6			5.5			183.6
Net loss per common share, basic and diluted	$	(1.35	)	$	(1.35	)	$	(0.57	)	$	(0.57	)	$	(1.11	)	$	(1.11	)

Since the Company was in a loss position for all periods presented, basic net loss per share attributable to common stockholders is the same as diluted net loss per share for all periods as the inclusion of all potential common shares outstanding would have been anti-dilutive. The weighted-average impact of potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:



	Year ended December 31,
	2018	2017	2016
Convertible preferred stock	—	147.6	147.6
Restricted stock units	35.0	52.7	47.9
Options to purchase shares of common stock	4.0	5.1	7.9
Co-Founder Grants⁽¹⁾	14.7	0.8	—
Shares subject to repurchase from early-exercised options and unvested restricted stock	0.1	0.2	0.9
Total	53.8	206.4	204.3


⁽¹⁾	In December 2017, the Board of Directors approved a grant to the Company’s co-founders of non-Plan RSAs with respect to 14.7 million shares of Class A Common Stock. The table above reflects the weighted-average impact for the period they were outstanding for the year ended December 31, 2017. See Note 11 "Stockholders' Equity" for further details.