Lately, I’ve seen a lot of people asking this question. The answer varies quite a bit, so let me be more definitive.
A blog post is as long as you need it to be to make your point, and no more.
But what about the search engines? What about the research about most clicked posts?
Forget them. They measured content that you didn’t write, for people who you don’t care about. It’s like averaging the height of the top 100 chess Grandmasters, and telling you that the optimum player is 5′ 7″.
I’ve had posts that went 2,000 words. (1,988 — close enough.) And I’ve had posts with zero words. (Eleven Words Guaranteed To Generate Killer Search Engine Traffic and Clicks)
Write until you say what needs to be said.