If you use WooCommerce 3.3.x then use WordPress Customizer (it’s a feature in the WordPress admin) to change the catalog and single product Image settings.
Go to Appearance > Customize > WooCommerce > Product Images
To change the product widget image size go to Settings > Media > Thumbnails Size.
More information about product image settings can be found in WooCommerce Documentation.
Note: After these changes, you need to Regenerate Thumbnails to apply them! You can use
Regenerate thumbnails plugin to do this.
