A bunch of numbers get thrown around for this, and it really depends on what you're counting as the core trilogy. The most common figure I see, and the one that feels solid, is about 481,000 words for the three volumes of 'The Lord of the Rings' combined. That's the text from 'The Fellowship of the Ring', 'The Two Towers', and 'The Return of the King' as published in most modern single-volume editions. People sometimes forget this isn't a trilogy in the modern sense; Tolkien wrote it as one giant book that got split for post-war paper rationing.
Where it gets fuzzy is the appendices. Do you count those? They add a significant chunk, maybe another 100,000 words of history, family trees, and linguistic notes. If you're talking pure narrative from "Concerning Hobbits" to the Grey Havens, stick with the 481k. I did a rough check once by comparing standard paperback page counts to average words-per-page estimates, and it landed right in that ballpark. It’s a commitment, but the density of the world-building makes it feel even longer in the best way possible. I always need a palate cleanser with a faster plot after a reread.