Thumbnail image sizes

In your admin panel you will see in Settings > Media the three different sizes being generated for each image you upload.

What do you mean you have to delete some space?

In dashboard go to setting -> media. Here you can see 3 different sizes.

thank you.

I used a regenerate thumbnail plugin, and now I have about 20000 images which I think are not being used. their sizes are different with those three sizes in my media setting. Is it safe to delete them?
Now every single image has 8 different sizes and I think some of them are not being used.

regenerate thumbnails plugin does not delete the old sizes, but only adds to them giving you more images total.

You can try looking thru this search results and finding a solution that might work for you: https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=how%20to%20delete%20unuzed%20image%20sizes%20in%20wordpress

great , thank you for the help