It’s fair to say that providing a guest checkout is widely considered best practice, and this will boost page level conversions of these shoppers that want to see the total order value (e.g. shipping and handling costs) prior to committing. Whether this changes the overall end-to-end conversion rate is more debatable.

Ultimately all purchasers of goods (that are going to be shipped) will need to give a physical delivery address and payment details, and an email address for a confirmation. So the key question is where in the shopping cart process you capture these details. A guest checkout should streamline and defer the capture of this data until the last moment.

It is also worth looking at where the cost of shipping is provided. If this is not on the product detail page, then this will definitely cause a spike in your abandonment rate, and then providing a guest checkout will definitely get more people to go further down the conversion path, but not necessarily to buy.

Charles