Hello,
WooCommerce has a few types of images that are generated for every product and used depending on the situation: 1) Original image (This type is used for zoom option and lightbox https://gyazo.com/ece404a20d9b5d45efd806562c6126a8 ) 2) Single product image size based on WC options (http://prntscr.com/o4cn5k) and WC use this image for the Product image on the single product page http://prntscr.com/o4cns2 3) Grid image http://prntscr.com/o4cob3 used for the all the images on grid (Products elements, Shop grid, Product category, Related product sliders etc) http://prntscr.com/o4cown
If you want to have zoom option you should keep images larger that single product box. If you don’t need zoom then you can resize original images. Hope my answer is clear.
Regards
