12. Net Loss Per Share Attributable to Common Stockholders

The following table presents the calculation of basic and diluted net loss per common share for the years ended December 31, 2018 and 2017:



	Years Ended December 31,
	2018		2017
Net loss attributable to common stockholders (basic)		(32,146,057)	$	(21,968,614)
Shares used to compute net loss per common share, basic and diluted		14,681,044		2,895,729
Net loss per share attributable to common stockholders, basic and diluted	$	(2.19)	$	(7.59)

Basic net loss per share is calculated by dividing net loss by the weighted-average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common shares and common share equivalents outstanding for the period. Common stock equivalents are only included when their effect is dilutive. The Company's potentially dilutive securities which include stock options, convertible preferred stock and common stock warrants have been excluded from the computation of diluted net loss per share as they would be anti-dilutive. For all periods presented, there is no difference in the number of shares used to compute basic and diluted shares outstanding due to the Company's net loss position.

The following outstanding common stock equivalents have been excluded from diluted net loss per common share for the years ended December 31, 2018 and 2017 because their inclusion would be anti-dilutive:


	December 31,	December 31,
	2018	2017
Options issued and outstanding	2,944,148	3,444,663
Warrants to purchase common stock	2,427,653	4,820,025
Restricted stock units	392,904	5,893,849
Total	5,764,705	14,158,537