About 157 million of
That's nearly 16 percent of its global user base that ONLY looks at the social network on a phone or a tablet, and never on an old fashioned-web page delivered on a desktop computer.
Unsurprisingly, Facebook now also collects 23 percent of its ad revenue from serving mobile ads. Total revenue was $1.59 billion, of which total ad revenue was $1.33 billion — implying that mobile revenue in Q4 was ~$300 million in the quarter.
Here's a chart of Facebook's mobile-only user base:
