The honest answer is it depends on the focus of the site and the general design and the demographics of the user base.
Here is the list of steps I would suggest to figure out this problem
Establish the maximum resolution which you plan to support by looking at the user demographics and analytics if available. This would help you establish your maximum resolution from a grid or media query perspective.
Depending on the focus of your website, define what are the sizes of the images you need to show. In an ecommerce site it is highly recommended to have crisp and visble images as they help define the decision making of the users and you might find out based upon your product, you might need to with larger or smaller images. To quote this article
In usability testing, users glean product details from images,
including details that aren’t covered in the product description.
Large images can show more detail, and multiple views offer even more
information. Pictures of products in use or in context go a long way
to answering customer questions. We’ve seen a user realize that a
toaster had big enough slots for bagels and another know that coasters
had feet that would protect her wooden furniture, simply by looking at
The increase in image size is not only seen on product pages. Category
pages, which often cram as many tiny images of products on one page as
possible, are also using larger images. This lets user see detail
early on in the shopping and comparison process, helping users spend
their time exploring the right products.
For example if you are showing deals on products and want to highlight the products very clearly, you might go with large displays like this which allow you to show only two images side by side
however if you are going to show objects which dont need to be so detailed a smaller image set might work with this like the example given below
- Hence based upon your product and the importance of product photography, you will need to decide how many products to show in a line while ensuring the corresponding gutter space is present between the products to enable the site to responsively scale as needed across mobile devices.
Here are examples of sites showing three,four and five products in one line ensuring there is sufficient breathing space between the products to allow the user to quickly scan the content.