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, 2019 and 2018:


	Year Ended
	December 31,
	2019		2018
Net loss attributable to common shareholders (basic and diluted)	$	(44,726,242)	$	(32,146,057)
Shares used to compute net loss per common share, basic and diluted		4,965,337		209,729
Net loss per share attributable to common shareholders, basic and diluted	$	(9.01)	$	(153.27)

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, RSUs 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, 2019 and 2018 because their inclusion would be anti-dilutive:


	December 31,	December 31,
	2019	2018
Options issued and outstanding	3,902,675	42,059
Restricted stock unit awards issued and outstanding	5,613	5,613
Warrants issued and outstanding	19,421,892	34,682
Series A convertible preferred stock	473,565	47,357
Series B convertible preferred stock	985,500	—
Series B-2 convertible preferred stock	1,931,350	—
Total	26,720,595	129,711