As of 3 July 2023, Special:Statistics showed 4,391,798,880 words across 6,678,098 articles implying an average of 658 words per article.
As of 2021, 33.997 GB (=33,997,900,893 bytes) across four billion words, implying 8.3 bytes/word. ASCII uses 1 byte/character which in turn implies 8.3 characters/word. However, this includes wikimarkup, and 5 char/word plus one for space or punctuation mark is standard, so 6 characters/word will be assumed.
There are currently 6,804,451 articles, which means 4.47487915564×10^9 words, which means 2.684927493384×10^10 characters.
One volume: 25cm high, 5cm thick. 500 leaves, 2 pagefaces per leaf, 2 columns per pageface, 80 rows/column, 50 characters per row. So one volume = 8,000,000 characters, or 1,333,333 words, or 2,027.5 articles. (Pictures not included!)
Sanity check: Encyclopædia Britannica has 44 million words across 32 volumes, or 1,375,000 words per volume.
Thus, the text of the English Wikipedia is currently equivalent to 3,356.2 volumes of Encyclopædia Britannica.
In other words, Wikipedia is approximately 104.88 times the size of Encyclopædia Britannica and that's excluding pictures for Wikipedia.