There’s no set rule. I typically target 250-400 words. That’s long enough to express one idea and short enough to discourage you from going off on tangents. I don’t like tangents in blog posts. Posts should be narrowly focused to make them easy for readers to absorb.
You’ll find opinions all over the place about blog post length. Most of you are busy, so I encourage you to keep your posts short to help you keep on a blogging schedule.
Let me know if you have questions!