Word count is easy to measure, which is probably why it became such a common content target. Unfortunately, a longer page is not automatically a better page.
Begin with the page purpose
A service page, product category, local landing page and educational guide all have different jobs. The content should be designed around that job before anybody decides how long it should be.
Ask what the visitor is trying to achieve, what they need to understand before taking the next step and what would make the page genuinely more useful than the alternatives.
Use search research to understand demand
Keyword data can reveal the language customers use, related questions and the way search demand is grouped. Competitor pages can also show what information is commonly expected.
Research should inform the brief, not dictate it. Repeating every related phrase usually makes the writing worse rather than more relevant.
Give each section a reason to exist
Strong pages tend to have a clear progression. They explain the offer, answer objections, provide evidence, clarify the process and help the reader decide what to do next.
If a section does not help the customer or strengthen the page meaning, it probably does not need to be there.
Build credibility into the content
Specific examples, process detail, genuine expertise and evidence usually do more for a page than another generic paragraph about quality service.
This is particularly important on competitive commercial pages, where many businesses say essentially the same thing.
Connect the page to the wider site
Internal links, related services and supporting guides help customers move naturally through the website while also making page relationships clearer to search engines.
Good content should strengthen the wider site rather than exist as an isolated document.
Improve from evidence
Publishing is not the end of the process. Search performance, engagement and conversion behaviour can show where a page is still unclear or where additional information would help.
The right length is simply the amount of content required to do the job properly.