ACF Image Sizes allows you to choose which image sizes are generated for ACF image and gallery fields. This approach means you won’t end up with image sizes that you just don’t need, which can save a considerable amount of space on your server and CDN.
Note: Until ACF 5 is released, this plugin only works with ACF Pro.
How does it work?
When you create an ACF image or gallery field type, there will be a list of all available image sizes. Check the sizes you want to create, now when you upload images to those fields, only the selected sizes will be created.
If you already have a site with ACF fields, you can use the bulk optimiser to remove or add images based on your selections.
Edit your ACF fields to select the image sizes you want, then go to Tools > ACF Image Sizes to run the bulk optimiser.