There are many possible elements that can increase the size, weight and load of a web and WordPress ] does not escape from this danger. In fact, there are default behaviors of our beloved CMS that contribute to overload the size of your website .
One of these default WordPress behaviors that contribute to occupy extra space in your installation is ] the management that makes the images you upload . Let me explain …
Every time you upload an image to illustrate an entry, WordPress automatically creates other sizes smaller than the one you have uploaded. The idea is good, do not believe, because it is based on the fact that you do not need to use in your publication the full size of the images you upload resized by HTML (you know, it is pulling or shrinking the image ) but it is better to use a version that better fits the width of your WordPress theme and in the process you reduce the loading time of your cover (especially).
To give an example; imagine that you have a great holiday photo of about 4,000 pixels that weighs 8 Mb. If you upload it to an entry and publish it as is, even if you reduce the size from the object editor, in reality you will be showing fewer pixels width and height but the image will weigh the same when it is displayed on your website, I remind you, nothing less than 8 Mb .
Now add how long it will take to load the cover of your website if you do the same at each entrance of the ¿10? that you show in it. That's it.
That's why WordPress automatically creates small copies of your images, so you use a size more appropriate to the width of your theme and, consequently, also of less weight in " ] megas ".
The idea is good on that side, but it turns out that, at the same time, too is taking up disk space from your highly-appreciated – and usually expensive – web hosting plan , then you will find 3 or 4 more images, which you do not always use.
And, say, if you never use the average size would not it be better to tell WordPress not to create that copy? or the big size, or whatever you want. I do not recommend removing the miniature size, because if you use the galleries is the one you will use.
Getting it is very simple just go on your WordPress Desktop to the side menu " Settings -> Media "and simply set to" zero "the size or sizes you do not want WordPress to automatically create.
Maybe you'll find it too radical, but if you think about it why are you going to upload the 8 Mb photo? Would not it be better to reduce the pixels before uploading it?
Normally, except in places dedicated to photography, it is never necessary to upload images of more size than the one that will normally show your WordPress theme so will not it be better not to unnecessarily occupy the expensive hosting space?.  At your home I leave the decision, but you know how to do it, and it's easy.