Choose a blog post length for SEO goals.
Post length should be set by what the topic needs, and there are two independent ways to estimate that. The first is competitive: what already ranks tells you the depth searchers and search engines currently reward, adjusted by post type — a news update needs well under half a pillar guide's length. The second is structural: count the subtopics you must cover and allow roughly 230 words each plus an introduction, because a subtopic given 80 words has not actually been answered. Taking the higher of the two prevents both under-covering the topic and padding to hit an arbitrary word count, which is the failure mode of length-first content planning.
Competitive target
Words = competitor average x goal factor
Structural target
Words = subtopics x 230 + 250 intro; take the higher of the two
Not intrinsically. The correlation between length and ranking exists because thorough coverage of a topic tends to require more words, not because word count is rewarded. Padding a 900-word answer to 2500 makes it worse, and dwell time and satisfaction signals will reflect that.
They catch different failures. The competitive figure stops you publishing something too thin to compete. The structural figure stops you publishing a long piece that still skips subtopics readers came for. Whichever is higher is the binding constraint on being genuinely useful.