It is common when adding various images on your products, depending on your WooCommerce settings, to have cropped images that don’t look as you need. Also, you may have imported images but now you need to change the size of the thumbnails. Thankfully there is a way to fix images, even after uploading them on your products.
First, log in to your installation and go to WooCommerce Settings > Products > Display
Under the Product Images section, you will find the Catalog Images, Single Product Images, and Product Thumbnails dimension input fields. Enter a value for Width and Height (in pixels)
Catalog Image is used for your images on the shop page and for shortcodes. Single Product Image is used for your images on the single product pages. Product Thumbnail is used for your smaller product thumbnails for widgets.
The images you upload to products will be resized to match the new values. If your settings are 100×100 and you upload a 300×600 image it will be resized to 100×200. There is also a ‘hard crop’ option where the images will be forced to the size specified in these settings, regardless of the raw image you upload. Note that the plugin will try to keep a reasonable resolution.
The minimum suggested width for images is 500px. Don’t change the Height field if you don’t want a crop effect.
After you’ve entered the sizes you need, click on Save Changes
The last step is to regenerate the thumbnails with the newly updated settings. A plugin is required for this. Go to plugins and install the Regenerate Thumbnails plugin. You can keep it for future use or remove it after fixing the thumbnails and you are not planning to change those settings again.