Basic net loss per share is determined by dividing net loss by the weighted average shares of common stock outstanding during the period, without consideration of potentially dilutive securities, except for those shares that are issuable for little or no cash consideration. Diluted net loss per share is determined by dividing net loss by diluted weighted average shares outstanding. Diluted weighted average shares reflects the dilutive effect, if any, of potentially dilutive common shares, such as stock options and warrants calculated using the treasury stock method. In periods with reported net operating losses, all common stock options and warrants are generally deemed anti-dilutive such that basic net loss per share and diluted net loss per share are equal.

The following potentially dilutive securities were excluded from the computation of earnings per share as of March 31, 2021 and 2020 because their effects would be anti-dilutive:

	March 31,
	2021		2020
Stock options		1,078,499		1,640
Common stock warrants - equity		3,994,107		1,826,599
Common stock reserved for conversion of preferred shares		2,048,101		1,799,093
Assumed conversion of convertible notes		146,288		63,493
Total		7,266,995		3,690,825

At March 31, 2021, the Company had 371,000 pre-funded warrants outstanding. The following table provides a reconciliation of the weighted average shares outstanding calculation for the three months ended March 31, 2021 and 2020:

	Three months ended March 31,
	2021		2020
Weighted average shares issued		6,125,922		72,740
Weighted average pre-funded warrants		371,000		-
Weighted average shares outstanding		6,496,922		72,740