Got myself confused re the image size I should upload for a product

[500N]

I am redoing one web site after losing my last one and the administrator who used to tell me what to set the optimum size of the image to prior to upload so it wasn't too big, took too much time to load etc.

I have read most of the threads and other useful bits on here but I have got myself confused re the image size I should upload for a product, partly because of all I have read re Small, Medium and Large !

I am fully conversant with Photoshop and image sizes, pixels etc and can resize images and resolution
to anything needed.

I haven't changed any of the settings / sizes in - Configuration - Images.


So, if I have a product photo on my hard drive - some are from 2 - 5Mb, what should I scale / resize it to in Photoshop BEFORE I upload it, for optimum performance on my web site (taking into account some people still use dial up) and also so I don't end up taking more space than required on the server.

Sorry for what is a basic question !

Thank you in anticipation.