This gauge is based on some estimates of how many words I produce in my archaic long-hand, double-spaced mode of writing first draft– it’s about 90 words to the page, based on past performance.
The ideal goal for the novel is 80,000 words. Once we’re out of the red, the old-school concept of a novel as a work of about 65,000 words is satisfied (with the proviso for estimated words/page, of course). Anywhere in the green zone is safe to stop– that’s not less than 70,000 words, which is really plenty. I’ll leave it to Stephen King and George R.R. Martin to write the really big books for the moment, as it’s not (yet)† my full-time job.
†For those who are curious: the writing part of my day is, alas, the lunch break from the actual full-time job which largely pays the bills, during which I also try to eat something. This means an average of not quite 40 minutes of productive writing, five days a week, with little bits infrequently shoe-horned in during weekends and
home repair events vacations. Between 2014 and 2016, this approach produced a bit more than 125,000 words of finished text (some of which appear on this very site!), which I my research suggests is not too far off of Martin’s Song of Ice and Fire pace as far as words/year goes. Slow and steady, as the saying goes….