Basic net loss per common share is computed by dividing net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share is computed by giving effect to all potential dilutive shares of common stock. Basic and diluted net loss per share of common stock were the same for all periods presented as the impact of all potentially dilutive securities outstanding was anti-dilutive. As it relates to the Notes, the Company uses the if converted method for calculating any potential dilutive effect on diluted loss per share.

The following common equivalent shares were excluded from the diluted net loss per share calculation because their inclusion would have been anti-dilutive:

	Year Ended December 31,
	2018		2017		2016
Stock options		1,746,073		2,440,290		1,884,425
Shares to be issued under ESPP		22,683		44,320		83,790
Restricted stock units		793,518		784,000		—
Convertible senior notes		3,411,199		3,411,199		—
Total		5,973,473		6,679,809		1,968,215

The Company is required to reserve and keep available from the Company’s authorized but unissued shares of common stock a number of shares equal to the number of shares subject to outstanding awards under the 2008 Plan and the number of shares reserved for issuance under each of the 2016 Plan and 2016 ESPP.

In connection with the issuance of the Notes in November 2017, the Company paid $12.9 million to enter into capped call option agreements to reduce the potential dilution to holders of the Company’s common stock upon conversion of the Notes. The capped call option agreements are excluded from the calculation of diluted net loss per share attributable to common stockholders as their effect is antidilutive.

The Company is required to reserve and keep available out of its authorized but unissued shares of common stock such number of shares sufficient for the exercise of all shares granted and available for grant under the Company’s 2008 Plan, 2016 Plan and 2016 ESPP.

The amount of such shares of the Company’s common stock reserved for these purposes at December 31, 2018 is as follows:

	Number of Shares
Stock options issued and outstanding		1,746,073
Additional shares available for grant under equity plans		1,808,539
Total		3,554,612