The stock may be on an upward tear, but Facebook, Inc. (FB) - Get Report is still too cheap, according to TheStreet's founder Jim Cramer.

Facebook is up 38.11% year-to-date, growing steadily ever since it got off to a rocky start in its first few years on the market. Despite those sky-rocketing returns, Cramer's calculations suggest there is still room to grow.

"Facebook is supposed to earn about eight bucks, according to my calculations, eight bucks in 2019," Cramer said during a web conference with Action Alerts PLUS members Wednesday, July 12. "So the stock is at $158 - 20 times 2019 earnings is too cheap, so I am saying that you should own Facebook."

Analysts estimate that Facebook will post earnings-per-share of about $7.55 in 2019, according to FactSet, with estimates ranging from $5.70 on the low side to $8.57 at the ceiling.

Advertising is projected to lead the boom, with mobile advertising in particular expected to drive profits for the company. Mobile advertising, which represented $22 million in revenue for the company last year, could more than double to $54 million in 2019, if analyst estimates are correct.

Cramer said that investors may still want to trim the holding from their portfolios if they want to secure a profit, as the rapid ascent of the stock may have led some shareholders to be overly weighted in the tech company.

"Nobody ever got hurt taking a profit," he said.

Facebook's shares rose 0.2% to $159.26 by Thursday's close.

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Editors' pick: Originally published July 13.