Business owners often ask this as if there's a target number to hit. There isn't. The right number of photos is whatever's needed to give every page on the site something real to show, without repeating the same handful of images everywhere.
Think in terms of pages, not a total
A homepage needs a strong hero image and a few supporting shots. Each service page benefits from at least one photo specific to that service, ideally a real before-and-after if the work allows for it. An about or team page needs actual faces. Adding these up for a typical small business site usually lands somewhere between 15 and 40 photos, but the number follows the page count, not the other way around.
More variety beats more volume
Thirty photos of the same type of job from slightly different angles is less useful than fifteen photos covering a genuine range: different services, different projects, different conditions. Variety is what actually helps a visitor picture their own situation being handled well.
Keep collecting after launch
A website doesn't need every photo on day one. Building a habit of photographing finished work on every job, going forward, means the photo library keeps growing and pages can be refreshed with newer material over time instead of going stale.
Quality matters more than count
A handful of well-lit, real, relevant photos does more for a page than a large gallery of mediocre ones. Padding a page with filler photos to hit some perceived quota doesn't help conversion and can actually slow the page down. See image file size and website speed.
Questions
Is it bad to reuse the same photo on multiple pages?
Occasionally, for something like a hero background, it's fine. Reusing the same "proof of work" photo across every service page starts to undercut the specific credibility each page is trying to build.
What if I only have a handful of good photos right now?
Use what you actually have rather than padding with stock images, and prioritize getting photos from your next several jobs specifically to fill the gaps. See why stock photos hurt a local business more than they help.
Should every photo be professionally shot?
No. A mix works fine, and for most small businesses, real phone photos taken consistently outperform a one-time professional shoot that never gets updated. See should you hire a photographer, or is a phone enough?