No one knows but--like the universe-- either the web is REALLY infinite or it’s just TOO BIG to count. While the first Google index in 1998 had 26m pages, and by 2000 the index reached 1 billion, this year Google's web spiders identified more than 1 trillion unique URLs.
Each day Google does the computational equivalent of fully exploring every intersection of every road of a new “continent” about 50000X as big as USA with 50000X as many roads and intersections.
And that's not all the URLs: Google cut out unique pages for identical content, and they missed all that material on the Deep Web that Google doesn't reach. Like the universe that doesn’t stop expanding, the web is still growing by billions of pages each day.