TheStreet's Jim Cramer, co-manager of the Action Alerts PLUS portfolio, and Research Director Jack Mohr love Facebook (FB - Get Report) for its 43% sales growth and strong long-term earnings power. They also like that the company has 1.5 billion engaged users on its platform. 

So what's not to love?

Over and over investors question the stock's valuation, something they should be careful doing, according to Cramer. 

If investors don't value Facebook on the "out years," they'll end up missing out on the stock because they think it's too expensive. 

But when Facebook is valued based on 2018 earnings estimates, the stock only trades at 30 times earnings.

"Do not value Facebook on 2016 numbers," Cramer cautioned, noting that he's been long the stock for most of its multi-year rally because of his long-term assessment. 

Facebook is a holding in Jim Cramer's Action Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells FB? Learn more now.

Cramer explained that "it's entirely possible" that Facebook could earn $6 per share in 2018. With the stock currently trading around $112, the valuation now ends up looking far too low. 

While analysts are looking for 2018 earnings to be near $5.50 per share, Cramer and Mohr think the company will do better than that. 

Facebook continues to top estimates, and its earnings situation is very compelling, Mohr said. Each selloff has been a great buying opportunity. 

At the time of publication, Cramer's Action Alerts PLUS had a long position in FB.