9. Net loss per share

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2019		2018		2019		2018
Numerator:
Net loss	$	(7,228)	$	(8,673)	$	(12,590)	$	(9,094)
Accretion of redeemable convertible preferred stock to redemption value		—		(70)		—		(70)
Net loss attributable to common stockholders, basic and diluted	$	(7,228)	$	(8,743)	$	(12,590)	$	(9,164)
Denominator:
Weighted average common shares outstanding, basic and diluted		3,268,390		92,171		1,726,795		66,422
Net loss per share attributable to common stockholders, basic and diluted	$	(2.21)	$	(94.86)	$	(7.29)	$	(137.97)

The Company excluded 56,765 shares and 134,229 shares of restricted common stock, presented on a weighted average basis, from the calculations of basic net loss per share attributable to common stockholders for the three months ended June 30, 2019 and 2018, respectively, because those shares had not vested. The Company excluded 63,801 shares and 159,878 shares of restricted common stock, presented on a weighted average basis, from the calculations of basic net loss per share attributable to common stockholders for the six months ended June 30, 2019 and 2018, respectively, because those shares had not vested.

The Company’s potentially dilutive securities, which include stock options, unvested restricted common stock and redeemable convertible preferred stock, have been excluded from the computation of diluted net loss per share attributable to common stockholders as the effect would be to reduce the net loss per share. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:


	Three and six months ended
	June 30,
	2019	2018
Options to purchase common stock	2,420,508	—
Unvested restricted stock	539,827	108,486
Redeemable convertible preferred stock (as converted to common stock)	—	7,368,894
Total	2,960,335	7,477,380