There's no magic number, but there is a formula that works: a page for every service with real search demand, a page for every market you genuinely serve, and supporting content that answers the questions buyers ask before they call.
Start with services
List every service you actually sell and want more of. Each of those is a distinct search with distinct intent. A plumbing company selling drain cleaning, water heaters, sewer repair, and repiping has four different customers with four different urgency levels and four wildly different job values. One combined page serves none of them well.
Then add markets
If you serve eight cities, a single 'service area' page listing all eight in a paragraph won't rank in seven of them. Build a page per market — but only for markets where you'd genuinely take the work. Pages for towns you'd never drive to are thin by definition and won't hold up.
Then supporting content
Cost, process, timeline, and comparison questions all get searched before anyone contacts a company. These pages convert at lower rates but capture buyers earlier, and they're much less contested than the primary service terms.
What not to do
Don't pad. A page that exists only to hold a keyword will underperform and can drag down the pages around it. Every page should be one you'd be comfortable sending a customer to directly.
The right page count is whatever fully covers what you sell and where you sell it. Not one page more.
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