Net loss per share attributable to common stock is computed by dividing the net loss attributable to common stock by the weighted-average number of common shares outstanding. We have outstanding stock options, restricted stock units, options to purchase shares under our ESPP, convertible preferred stock, and convertible senior notes, which are considered in the calculation of diluted net income per share whenever doing so would be dilutive.

We calculate basic and diluted net loss per share attributable to common stock in conformity with the two-class method required for companies with participating securities. We consider our convertible preferred stock to be participating securities. Under the two-class method, net loss attributable to common stock is not allocated to the preferred stock as its holders do not have a contractual obligation to share in losses, as discussed in Note 11.

The calculation of basic and diluted net loss per share attributable to common stock was as follows:


	Three Months Ended March 31,
	2021		2020

Numerator:
Net loss	$	(35,784)	$	(60,117)
Dividends on convertible preferred stock	(2,336)		—
Net loss attributable to common stock—basic and diluted	$	(38,120)	$	(60,117)
Denominator:
Weighted average shares—basic and diluted(1)	103,427,764		93,442,706
Net loss per share attributable to common stock—basic and diluted	$	(0.37)	$	(0.64)

(1) Basic and diluted weighted average shares outstanding include (i) common stock earned but not yet issued related to share-based dividends on our convertible preferred stock, and (ii) restricted stock units that have vested but whose settlement into common stock were deferred at the option of certain non-employee directors.

The following outstanding shares of common stock equivalents were excluded from the computation of the diluted net loss per share for the periods presented because their effect would have been anti-dilutive:


	Three Months Ended March 31,
	2021	2020

2023 notes as if converted(1)	778,297	—
2025 notes as if converted	9,119,960	—
2027 notes as if converted	5,346,000	—
Convertible preferred stock as if converted	2,040,000	—
Stock options outstanding(2)	5,063,462	7,028,719
Restricted stock units outstanding(2)(3)	3,862,964	4,681,875
Employee stock purchase plan	128,032	233,416
Total	26,338,715	11,944,010

(1) Includes $39 principal amount of 2023 notes with respect to which we received conversion requests by March 31, 2021. See Note 1.

(2) Excludes 260,509 incremental PSUs and 150,000 incremental PSOs that could vest, assuming applicable performance criteria and market conditions are achieved at 200% of target, which is the maximum achievement level. See Note 12 for additional information regarding PSUs and PSOs.